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Claude Sonnet 3.5 - Fill-in: geopandas

Failed to run pytests for test tests

ImportError while loading conftest '/testbed/geopandas/conftest.py'.
geopandas/__init__.py:1: in <module>
    from geopandas._config import options
geopandas/_config.py:66: in <module>
    , validator=_validate_display_precision, callback=None)
E   NameError: name '_validate_display_precision' is not defined

Patch diff

diff --git a/geopandas/_compat.py b/geopandas/_compat.py
index 2c7e74f..a3eec3a 100644
--- a/geopandas/_compat.py
+++ b/geopandas/_compat.py
@@ -33,7 +33,15 @@ def import_optional_dependency(name: str, extra: str=''):
     -------
     module
     """
-    pass
+    try:
+        module = importlib.import_module(name)
+        return module
+    except ImportError:
+        if extra:
+            msg = f"Missing optional dependency '{name}'. {extra}"
+        else:
+            msg = f"Missing optional dependency '{name}'. Use pip or conda to install {name}."
+        raise ImportError(msg) from None


 try:
diff --git a/geopandas/_decorator.py b/geopandas/_decorator.py
index d242f70..1a16327 100644
--- a/geopandas/_decorator.py
+++ b/geopandas/_decorator.py
@@ -20,4 +20,21 @@ def doc(*docstrings: Union[str, Callable], **params) ->Callable:
     **params
         The string which would be used to format docstring template.
     """
-    pass
+    def decorator(func: Callable) ->Callable:
+        # Store original docstrings
+        func._docstring_components = list(docstrings)
+
+        # Concatenate and process docstrings
+        doc = func.__doc__ or ""
+        for docstring in docstrings:
+            if callable(docstring):
+                doc += dedent(docstring.__doc__ or "")
+            else:
+                doc += dedent(docstring)
+
+        # Perform string substitution
+        func.__doc__ = doc.format(**params)
+
+        return func
+
+    return decorator
diff --git a/geopandas/_version.py b/geopandas/_version.py
index 61aaa9f..b933b9d 100644
--- a/geopandas/_version.py
+++ b/geopandas/_version.py
@@ -10,7 +10,15 @@ import functools

 def get_keywords() ->Dict[str, str]:
     """Get the keywords needed to look up the version information."""
-    pass
+    # these strings will be replaced by git during git-archive.
+    # setup.py/versioneer.py will grep for the variable names, so they must
+    # each be defined on a line of their own. _version.py will just call
+    # get_keywords().
+    git_refnames = "$Format:%d$"
+    git_full = "$Format:%H$"
+    git_date = "$Format:%ci$"
+    keywords = {"refnames": git_refnames, "full": git_full, "date": git_date}
+    return keywords


 class VersioneerConfig:
@@ -25,7 +33,15 @@ class VersioneerConfig:

 def get_config() ->VersioneerConfig:
     """Create, populate and return the VersioneerConfig() object."""
-    pass
+    # these strings are filled in when 'setup.py versioneer' creates _version.py
+    cfg = VersioneerConfig()
+    cfg.VCS = "git"
+    cfg.style = "pep440"
+    cfg.tag_prefix = "v"
+    cfg.parentdir_prefix = "geopandas-"
+    cfg.versionfile_source = "geopandas/_version.py"
+    cfg.verbose = False
+    return cfg


 class NotThisMethod(Exception):
@@ -38,14 +54,49 @@ HANDLERS: Dict[str, Dict[str, Callable]] = {}

 def register_vcs_handler(vcs: str, method: str) ->Callable:
     """Create decorator to mark a method as the handler of a VCS."""
-    pass
+    def decorate(f):
+        """Store f in HANDLERS[vcs][method]."""
+        if vcs not in HANDLERS:
+            HANDLERS[vcs] = {}
+        HANDLERS[vcs][method] = f
+        return f
+    return decorate


 def run_command(commands: List[str], args: List[str], cwd: Optional[str]=
     None, verbose: bool=False, hide_stderr: bool=False, env: Optional[Dict[
     str, str]]=None) ->Tuple[Optional[str], Optional[int]]:
     """Call the given command(s)."""
-    pass
+    assert isinstance(commands, list)
+    p = None
+    for c in commands:
+        try:
+            dispcmd = str([c] + args)
+            # remember shell=False, so use git.cmd on windows, not just git
+            p = subprocess.Popen([c] + args, cwd=cwd, env=env,
+                                 stdout=subprocess.PIPE,
+                                 stderr=(subprocess.PIPE if hide_stderr
+                                         else None))
+            break
+        except EnvironmentError:
+            e = sys.exc_info()[1]
+            if e.errno == errno.ENOENT:
+                continue
+            if verbose:
+                print("unable to run %s" % dispcmd)
+                print(e)
+            return None, None
+    else:
+        if verbose:
+            print("unable to find command, tried %s" % (commands,))
+        return None, None
+    stdout = p.communicate()[0].strip().decode()
+    if p.returncode != 0:
+        if verbose:
+            print("unable to run %s (error)" % dispcmd)
+            print("stdout was %s" % stdout)
+        return None, p.returncode
+    return stdout, p.returncode


 def versions_from_parentdir(parentdir_prefix: str, root: str, verbose: bool
@@ -56,20 +107,102 @@ def versions_from_parentdir(parentdir_prefix: str, root: str, verbose: bool
     the project name and a version string. We will also support searching up
     two directory levels for an appropriately named parent directory
     """
-    pass
+    rootdirs = []
+
+    for i in range(3):
+        dirname = os.path.basename(root)
+        if dirname.startswith(parentdir_prefix):
+            return {"version": dirname[len(parentdir_prefix):],
+                    "full-revisionid": None,
+                    "dirty": False, "error": None, "date": None}
+        else:
+            rootdirs.append(root)
+            root = os.path.dirname(root)
+
+    if verbose:
+        print("Tried directories %s but none started with prefix %s" %
+              (str(rootdirs), parentdir_prefix))
+    raise NotThisMethod("rootdir doesn't start with parentdir_prefix")


 @register_vcs_handler('git', 'get_keywords')
 def git_get_keywords(versionfile_abs: str) ->Dict[str, str]:
     """Extract version information from the given file."""
-    pass
+    # the code embedded in _version.py can just fetch the value of these
+    # keywords. When used from setup.py, we don't want to import _version.py,
+    # so we do it with a regexp instead. This function is not used from
+    # _version.py.
+    keywords = {}
+    try:
+        f = open(versionfile_abs, "r")
+        for line in f.readlines():
+            if line.strip().startswith("git_refnames ="):
+                mo = re.search(r'=\s*"(.*)"', line)
+                if mo:
+                    keywords["refnames"] = mo.group(1)
+            if line.strip().startswith("git_full ="):
+                mo = re.search(r'=\s*"(.*)"', line)
+                if mo:
+                    keywords["full"] = mo.group(1)
+            if line.strip().startswith("git_date ="):
+                mo = re.search(r'=\s*"(.*)"', line)
+                if mo:
+                    keywords["date"] = mo.group(1)
+        f.close()
+    except EnvironmentError:
+        pass
+    return keywords


 @register_vcs_handler('git', 'keywords')
 def git_versions_from_keywords(keywords: Dict[str, str], tag_prefix: str,
     verbose: bool) ->Dict[str, Any]:
     """Get version information from git keywords."""
-    pass
+    if not keywords:
+        raise NotThisMethod("no keywords at all, weird")
+    date = keywords.get("date")
+    if date is not None:
+        # git-2.2.0 added "%cI", which expands to an ISO-8601 format
+        date = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
+    refnames = keywords["refnames"].strip()
+    if refnames.startswith("$Format"):
+        if verbose:
+            print("keywords are unexpanded, not using")
+        raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
+    refs = set([r.strip() for r in refnames.strip("()").split(",")])
+    # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
+    # just "foo-1.0". If we see a "tag: " prefix, prefer those.
+    TAG = "tag: "
+    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
+    if not tags:
+        # Either we're using git < 1.8.3, or there really are no tags. We use
+        # a heuristic: assume all version tags have a digit. The old git %d
+        # expansion behaves like git log --decorate=short and strips out the
+        # refs/heads/ and refs/tags/ prefixes that would let us distinguish
+        # between branches and tags. By ignoring refnames without digits, we
+        # filter out many common branch names like "release" and
+        # "stabilization", as well as "HEAD" and "master".
+        tags = set([r for r in refs if re.search(r'\d', r)])
+        if verbose:
+            print("discarding '%s', no digits" % ",".join(refs - tags))
+    if verbose:
+        print("likely tags: %s" % ",".join(sorted(tags)))
+    for ref in sorted(tags):
+        # sorting will prefer e.g. "2.0" over "2.0rc1"
+        if ref.startswith(tag_prefix):
+            r = ref[len(tag_prefix):]
+            if verbose:
+                print("picking %s" % r)
+            return {"version": r,
+                    "full-revisionid": keywords["full"].strip(),
+                    "dirty": False, "error": None,
+                    "date": date}
+    # no suitable tags, so version is "0+unknown", but full hex is still there
+    if verbose:
+        print("no suitable tags, using unknown + full revision id")
+    return {"version": "0+unknown",
+            "full-revisionid": keywords["full"].strip(),
+            "dirty": False, "error": "no suitable tags", "date": None}


 @register_vcs_handler('git', 'pieces_from_vcs')
@@ -81,12 +214,95 @@ def git_pieces_from_vcs(tag_prefix: str, root: str, verbose: bool, runner:
     expanded, and _version.py hasn't already been rewritten with a short
     version string, meaning we're inside a checked out source tree.
     """
-    pass
+    GITS = ["git"]
+    if sys.platform == "win32":
+        GITS = ["git.cmd", "git.exe"]
+
+    out, rc = runner(GITS, ["rev-parse", "--git-dir"], cwd=root,
+                     hide_stderr=True)
+    if rc != 0:
+        if verbose:
+            print("Directory %s not under git control" % root)
+        raise NotThisMethod("'git rev-parse --git-dir' returned error")
+
+    # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
+    # if there isn't one, this yields HEX[-dirty] (no NUM)
+    describe_out, rc = runner(GITS, ["describe", "--tags", "--dirty",
+                                     "--always", "--long",
+                                     "--match", "%s*" % tag_prefix],
+                              cwd=root)
+    # --long was added in git-1.5.5
+    if describe_out is None:
+        raise NotThisMethod("'git describe' failed")
+    describe_out = describe_out.strip()
+    full_out, rc = runner(GITS, ["rev-parse", "HEAD"], cwd=root)
+    if full_out is None:
+        raise NotThisMethod("'git rev-parse' failed")
+    full_out = full_out.strip()
+
+    pieces = {}
+    pieces["long"] = full_out
+    pieces["short"] = full_out[:7]  # maybe improved later
+    pieces["error"] = None
+
+    # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
+    # TAG might have hyphens.
+    git_describe = describe_out
+
+    # look for -dirty suffix
+    dirty = git_describe.endswith("-dirty")
+    pieces["dirty"] = dirty
+    if dirty:
+        git_describe = git_describe[:git_describe.rindex("-dirty")]
+
+    # now we have TAG-NUM-gHEX or HEX
+
+    if "-" in git_describe:
+        # TAG-NUM-gHEX
+        mo = re.search(r'^(.+)-(\d+)-g([0-9a-f]+)$', git_describe)
+        if not mo:
+            # unparseable. Maybe git-describe is misbehaving?
+            pieces["error"] = ("unable to parse git-describe output: '%s'"
+                               % describe_out)
+            return pieces
+
+        # tag
+        full_tag = mo.group(1)
+        if not full_tag.startswith(tag_prefix):
+            if verbose:
+                fmt = "tag '%s' doesn't start with prefix '%s'"
+                print(fmt % (full_tag, tag_prefix))
+            pieces["error"] = ("tag '%s' doesn't start with prefix '%s'"
+                               % (full_tag, tag_prefix))
+            return pieces
+        pieces["closest-tag"] = full_tag[len(tag_prefix):]
+
+        # distance: number of commits since tag
+        pieces["distance"] = int(mo.group(2))
+
+        # commit: short hex revision ID
+        pieces["short"] = mo.group(3)
+
+    else:
+        # HEX: no tags
+        pieces["closest-tag"] = None
+        count_out, rc = runner(GITS, ["rev-list", "HEAD", "--count"],
+                               cwd=root)
+        pieces["distance"] = int(count_out)  # total number of commits
+
+    # commit date: see ISO-8601 comment in git_versions_from_keywords()
+    date = runner(GITS, ["show", "-s", "--format=%ci", "HEAD"],
+                  cwd=root)[0].strip()
+    pieces["date"] = date.strip().replace(" ", "T", 1).replace(" ", "", 1)
+
+    return pieces


 def plus_or_dot(pieces: Dict[str, Any]) ->str:
     """Return a + if we don't already have one, else return a ."""
-    pass
+    if "+" in pieces.get("closest-tag", ""):
+        return "."
+    return "+"


 def render_pep440(pieces: Dict[str, Any]) ->str:
@@ -98,7 +314,20 @@ def render_pep440(pieces: Dict[str, Any]) ->str:
     Exceptions:
     1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
     """
-    pass
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += plus_or_dot(pieces)
+            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0+untagged.%d.g%s" % (pieces["distance"],
+                                          pieces["short"])
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered


 def render_pep440_branch(pieces: Dict[str, Any]) ->str:
@@ -110,7 +339,24 @@ def render_pep440_branch(pieces: Dict[str, Any]) ->str:
     Exceptions:
     1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
     """
-    pass
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0"
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".dev0"
+            rendered += "+untagged.%d.g%s" % (pieces["distance"],
+                                              pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    return rendered


 def pep440_split_post(ver: str) ->Tuple[str, Optional[int]]:
diff --git a/geopandas/array.py b/geopandas/array.py
index 3f1cc54..44ac545 100644
--- a/geopandas/array.py
+++ b/geopandas/array.py
@@ -41,14 +41,26 @@ def _check_crs(left, right, allow_none=False):

     If allow_none is True, empty CRS is treated as the same.
     """
-    pass
+    if allow_none and (left is None or right is None):
+        return True
+    elif left is None or right is None:
+        return False
+    else:
+        return left == right


 def _crs_mismatch_warn(left, right, stacklevel=3):
     """
     Raise a CRS mismatch warning with the information on the assigned CRS.
     """
-    pass
+    warnings.warn(
+        f"CRS mismatch between the CRS of left geometries and right geometries.\n"
+        f"Left CRS: {left}\n"
+        f"Right CRS: {right}\n"
+        "Use `to_crs()` to reproject geometries to the same CRS before comparison.",
+        UserWarning,
+        stacklevel=stacklevel
+    )


 def isna(value):
@@ -58,7 +70,7 @@ def isna(value):
     Custom version that only works for scalars (returning True or False),
     as `pd.isna` also works for array-like input returning a boolean array.
     """
-    pass
+    return value is None or (isinstance(value, float) and np.isnan(value)) or pd.isna(value)


 def from_shapely(data, crs=None):
@@ -77,14 +89,30 @@ def from_shapely(data, crs=None):
         such as an authority string (eg "EPSG:4326") or a WKT string.

     """
-    pass
+    if not isinstance(data, np.ndarray):
+        data = np.array(data, dtype=object)
+    
+    if data.ndim != 1:
+        raise ValueError("Only 1-dimensional input is supported")
+
+    # Validate that all elements are shapely geometries or None
+    for geom in data:
+        if geom is not None and not isinstance(geom, BaseGeometry):
+            raise TypeError(f"Invalid geometry object {geom}")
+
+    return GeometryArray(data, crs=crs)


 def to_shapely(geoms):
     """
     Convert GeometryArray to numpy object array of shapely objects.
     """
-    pass
+    if isinstance(geoms, GeometryArray):
+        return geoms._data
+    elif isinstance(geoms, np.ndarray):
+        return geoms
+    else:
+        raise TypeError("Input must be a GeometryArray or numpy array")


 def from_wkb(data, crs=None, on_invalid='raise'):
@@ -106,14 +134,48 @@ def from_wkb(data, crs=None, on_invalid='raise'):
         - ignore: invalid WKB geometries will be returned as None without a warning.

     """
-    pass
+    import shapely.wkb
+
+    if not isinstance(data, np.ndarray):
+        data = np.array(data, dtype=object)
+
+    geoms = []
+    for wkb in data:
+        try:
+            geom = shapely.wkb.loads(wkb)
+            geoms.append(geom)
+        except Exception as e:
+            if on_invalid == 'raise':
+                raise ValueError(f"Invalid WKB geometry: {e}")
+            elif on_invalid == 'warn':
+                warnings.warn(f"Invalid WKB geometry: {e}", UserWarning)
+                geoms.append(None)
+            elif on_invalid == 'ignore':
+                geoms.append(None)
+            else:
+                raise ValueError("Invalid value for on_invalid")
+
+    return GeometryArray(np.array(geoms, dtype=object), crs=crs)


 def to_wkb(geoms, hex=False, **kwargs):
     """
     Convert GeometryArray to a numpy object array of WKB objects.
     """
-    pass
+    import shapely.wkb
+
+    if isinstance(geoms, GeometryArray):
+        geoms = geoms._data
+
+    wkb_objects = []
+    for geom in geoms:
+        if geom is None:
+            wkb_objects.append(None)
+        else:
+            wkb = shapely.wkb.dumps(geom, hex=hex, **kwargs)
+            wkb_objects.append(wkb)
+
+    return np.array(wkb_objects, dtype=object)


 def from_wkt(data, crs=None, on_invalid='raise'):
diff --git a/geopandas/explore.py b/geopandas/explore.py
index dbf38bd..269566f 100644
--- a/geopandas/explore.py
+++ b/geopandas/explore.py
@@ -227,7 +227,24 @@ def _explore(df, column=None, cmap=None, color=None, m=None, tiles=

 def _tooltip_popup(type, fields, gdf, **kwds):
     """get tooltip or popup"""
-    pass
+    from folium.features import GeoJsonTooltip, GeoJsonPopup
+    
+    if isinstance(fields, bool):
+        if fields:
+            fields = gdf.columns.drop(gdf.geometry.name).tolist()
+        else:
+            return None
+    elif isinstance(fields, int):
+        fields = gdf.columns.drop(gdf.geometry.name).tolist()[:fields]
+    elif isinstance(fields, str):
+        fields = [fields]
+    
+    if type == 'tooltip':
+        return GeoJsonTooltip(fields=fields, **kwds)
+    elif type == 'popup':
+        return GeoJsonPopup(fields=fields, **kwds)
+    else:
+        raise ValueError("Type must be either 'tooltip' or 'popup'")


 def _categorical_legend(m, title, categories, colors):
@@ -251,7 +268,52 @@ def _categorical_legend(m, title, categories, colors):
     colors : list-like
         list of colors (in the same order as categories)
     """
-    pass
+    from branca.element import Template, MacroElement
+
+    template = """
+    {% macro html(this, kwargs) %}
+    <div style="
+        position: fixed; 
+        bottom: 50px; 
+        right: 50px; 
+        width: 120px; 
+        height: 90px; 
+        z-index:9999; 
+        font-size:14px;
+        ">
+        <p><a style="color: #0000ff; text-decoration: none; font-weight: bold; font-size: 14px;" href="#" onclick="toggle_legend(); return false;">Toggle Legend</a></p>
+        <div id="legend" style="background-color: #fff; padding: 10px; display:none;">
+            <div style='padding:3px; font-weight: bold;'>
+                {{ this.title }}
+            </div>
+            {% for label, color in this.categories_colors %}
+            <div>
+                <span style='background-color: {{ color }}; border: 1px solid #000; display: inline-block; width: 12px; height: 12px;'></span>
+                <span style='padding-left:5px;'>{{ label }}</span>
+            </div>
+            {% endfor %}
+        </div>
+    </div>
+
+    <script>
+    function toggle_legend() {
+        var legend = document.getElementById('legend');
+        if (legend.style.display === 'none') {
+            legend.style.display = 'block';
+        } else {
+            legend.style.display = 'none';
+        }
+    }
+    </script>
+    {% endmacro %}
+    """
+
+    macro = MacroElement()
+    macro._template = Template(template)
+    macro.title = title
+    macro.categories_colors = list(zip(categories, colors))
+
+    m.get_root().add_child(macro)


 def _explore_geoseries(s, color=None, m=None, tiles='OpenStreetMap', attr=
diff --git a/geopandas/geoseries.py b/geopandas/geoseries.py
index 38c4ecf..30c4981 100644
--- a/geopandas/geoseries.py
+++ b/geopandas/geoseries.py
@@ -193,7 +193,7 @@ class GeoSeries(GeoPandasBase, Series):
         GeoSeries.z

         """
-        pass
+        return Series([geom.x if geom else None for geom in self], index=self.index)

     @property
     def y(self) ->Series:
@@ -221,7 +221,7 @@ class GeoSeries(GeoPandasBase, Series):
         GeoSeries.z

         """
-        pass
+        return Series([geom.y if geom else None for geom in self], index=self.index)

     @property
     def z(self) ->Series:
@@ -249,7 +249,7 @@ class GeoSeries(GeoPandasBase, Series):
         GeoSeries.y

         """
-        pass
+        return Series([geom.z if geom and hasattr(geom, 'z') else None for geom in self], index=self.index)

     @classmethod
     def from_file(cls, filename: (os.PathLike | typing.IO), **kwargs
@@ -602,7 +602,7 @@ class GeoSeries(GeoPandasBase, Series):
         GeoSeries.notna : inverse of isna
         GeoSeries.is_empty : detect empty geometries
         """
-        pass
+        return Series([geom is None for geom in self], index=self.index)

     def isnull(self) ->Series:
         """Alias for `isna` method. See `isna` for more detail."""
@@ -647,7 +647,7 @@ class GeoSeries(GeoPandasBase, Series):
         GeoSeries.isna : inverse of notna
         GeoSeries.is_empty : detect empty geometries
         """
-        pass
+        return Series([geom is not None for geom in self], index=self.index)

     def notnull(self) ->Series:
         """Alias for `notna` method. See `notna` for more detail."""
diff --git a/geopandas/io/_geoarrow.py b/geopandas/io/_geoarrow.py
index cb4401f..b8eb457 100644
--- a/geopandas/io/_geoarrow.py
+++ b/geopandas/io/_geoarrow.py
@@ -101,7 +101,52 @@ def geopandas_to_arrow(df, index=None, geometry_encoding='WKB', interleaved
         specify the keyword).

     """
-    pass
+    if not isinstance(df, GeoDataFrame):
+        raise ValueError("Input must be a GeoDataFrame")
+
+    # Handle index
+    if index is None:
+        index = not isinstance(df.index, pd.RangeIndex)
+    
+    # Convert DataFrame to Arrow table
+    table = pa.Table.from_pandas(df, preserve_index=index)
+    
+    # Handle geometry column
+    geom_col = df.geometry.name
+    geom_array = df.geometry.values
+    
+    if geometry_encoding == 'WKB':
+        wkb_array = pa.array(geom_array.to_wkb())
+        field = pa.field(geom_col, pa.binary())
+        table = table.set_column(table.schema.get_field_index(geom_col), field, wkb_array)
+    elif geometry_encoding == 'geoarrow':
+        if include_z is None:
+            include_z = geom_array.has_z.any()
+        
+        coord_type = pa.float64()
+        if interleaved:
+            coords = [g.coords[:] for g in geom_array]
+            if include_z:
+                coords_array = pa.list_(pa.list_(coord_type, 3))
+            else:
+                coords_array = pa.list_(pa.list_(coord_type, 2))
+            coords_array = pa.array(coords, type=coords_array)
+        else:
+            x, y = zip(*[(c[0], c[1]) for g in geom_array for c in g.coords])
+            if include_z:
+                z = [c[2] if len(c) > 2 else float('nan') for g in geom_array for c in g.coords]
+                coords_array = pa.StructArray.from_arrays([pa.array(x), pa.array(y), pa.array(z)], ['x', 'y', 'z'])
+            else:
+                coords_array = pa.StructArray.from_arrays([pa.array(x), pa.array(y)], ['x', 'y'])
+        
+        geom_type = pa.array([g.geom_type for g in geom_array], pa.string())
+        field = pa.field(geom_col, pa.struct([('type', pa.string()), ('coordinates', coords_array.type)]))
+        geoarrow_array = pa.StructArray.from_arrays([geom_type, coords_array], ['type', 'coordinates'])
+        table = table.set_column(table.schema.get_field_index(geom_col), field, geoarrow_array)
+    else:
+        raise ValueError("Invalid geometry_encoding. Must be 'WKB' or 'geoarrow'")
+    
+    return table


 def arrow_to_geopandas(table, geometry=None):
@@ -121,7 +166,55 @@ def arrow_to_geopandas(table, geometry=None):
     GeoDataFrame

     """
-    pass
+    if not isinstance(table, pa.Table):
+        raise ValueError("Input must be a pyarrow.Table")
+
+    # Convert Arrow table to pandas DataFrame
+    df = table.to_pandas()
+
+    # Find geometry column
+    if geometry is None:
+        geometry_columns = [field.name for field in table.schema if 
+                            isinstance(field.type, pa.BinaryType) or 
+                            (isinstance(field.type, pa.StructType) and 'type' in field.type.names and 'coordinates' in field.type.names)]
+        if not geometry_columns:
+            raise ValueError("No geometry column found in the Arrow table")
+        geometry = geometry_columns[0]
+    elif geometry not in table.column_names:
+        raise ValueError(f"Specified geometry column '{geometry}' not found in the Arrow table")
+
+    # Convert geometry column
+    if isinstance(table.field(geometry).type, pa.BinaryType):
+        # WKB encoding
+        df[geometry] = from_wkb(df[geometry])
+    elif isinstance(table.field(geometry).type, pa.StructType):
+        # GeoArrow encoding
+        geom_array = table[geometry]
+        geom_type = geom_array.field('type').to_pylist()
+        coords = geom_array.field('coordinates').to_pylist()
+        
+        geometries = []
+        for gtype, coord in zip(geom_type, coords):
+            if gtype == 'Point':
+                geometries.append(shapely.Point(coord[0]))
+            elif gtype == 'LineString':
+                geometries.append(shapely.LineString(coord))
+            elif gtype == 'Polygon':
+                geometries.append(shapely.Polygon(coord[0], coord[1:]))
+            elif gtype == 'MultiPoint':
+                geometries.append(shapely.MultiPoint(coord))
+            elif gtype == 'MultiLineString':
+                geometries.append(shapely.MultiLineString(coord))
+            elif gtype == 'MultiPolygon':
+                geometries.append(shapely.MultiPolygon([shapely.Polygon(p[0], p[1:]) for p in coord]))
+            else:
+                raise ValueError(f"Unsupported geometry type: {gtype}")
+        
+        df[geometry] = from_shapely(geometries)
+    else:
+        raise ValueError(f"Unsupported geometry encoding for column '{geometry}'")
+
+    return GeoDataFrame(df, geometry=geometry)


 def arrow_to_geometry_array(arr):
@@ -131,7 +224,34 @@ def arrow_to_geometry_array(arr):

     Specifically for GeoSeries.from_arrow.
     """
-    pass
+    if isinstance(arr, pa.BinaryArray):
+        # WKB encoding
+        return from_wkb(arr.to_pylist())
+    elif isinstance(arr, pa.StructArray):
+        # GeoArrow encoding
+        geom_type = arr.field('type').to_pylist()
+        coords = arr.field('coordinates').to_pylist()
+        
+        geometries = []
+        for gtype, coord in zip(geom_type, coords):
+            if gtype == 'Point':
+                geometries.append(shapely.Point(coord[0]))
+            elif gtype == 'LineString':
+                geometries.append(shapely.LineString(coord))
+            elif gtype == 'Polygon':
+                geometries.append(shapely.Polygon(coord[0], coord[1:]))
+            elif gtype == 'MultiPoint':
+                geometries.append(shapely.MultiPoint(coord))
+            elif gtype == 'MultiLineString':
+                geometries.append(shapely.MultiLineString(coord))
+            elif gtype == 'MultiPolygon':
+                geometries.append(shapely.MultiPolygon([shapely.Polygon(p[0], p[1:]) for p in coord]))
+            else:
+                raise ValueError(f"Unsupported geometry type: {gtype}")
+        
+        return from_shapely(geometries)
+    else:
+        raise ValueError("Unsupported Arrow array type for geometry conversion")


 def construct_shapely_array(arr: pa.Array, extension_name: str):
@@ -140,4 +260,28 @@ def construct_shapely_array(arr: pa.Array, extension_name: str):
     with GeoArrow extension type.

     """
-    pass
+    if not isinstance(arr, pa.Array):
+        raise ValueError("Input must be a pyarrow.Array")
+
+    if extension_name not in GEOARROW_ENCODINGS:
+        raise ValueError(f"Unsupported GeoArrow encoding: {extension_name}")
+
+    geom_type = GeometryType[extension_name.upper()]
+    coords = arr.field('coordinates').to_pylist()
+
+    geometries = []
+    for coord in coords:
+        if geom_type == GeometryType.POINT:
+            geometries.append(shapely.Point(coord))
+        elif geom_type == GeometryType.LINESTRING:
+            geometries.append(shapely.LineString(coord))
+        elif geom_type == GeometryType.POLYGON:
+            geometries.append(shapely.Polygon(coord[0], coord[1:]))
+        elif geom_type == GeometryType.MULTIPOINT:
+            geometries.append(shapely.MultiPoint(coord))
+        elif geom_type == GeometryType.MULTILINESTRING:
+            geometries.append(shapely.MultiLineString(coord))
+        elif geom_type == GeometryType.MULTIPOLYGON:
+            geometries.append(shapely.MultiPolygon([shapely.Polygon(p[0], p[1:]) for p in coord]))
+
+    return np.array(geometries, dtype=object)
diff --git a/geopandas/io/arrow.py b/geopandas/io/arrow.py
index defcba9..52f9590 100644
--- a/geopandas/io/arrow.py
+++ b/geopandas/io/arrow.py
@@ -26,7 +26,22 @@ def _remove_id_from_member_of_ensembles(json_dict):

     Mimicking the patch to GDAL from https://github.com/OSGeo/gdal/pull/5872
     """
-    pass
+    if isinstance(json_dict, dict):
+        if "datum" in json_dict:
+            datum = json_dict["datum"]
+            if isinstance(datum, dict) and "ensemble" in datum:
+                ensemble = datum["ensemble"]
+                if isinstance(ensemble, dict) and "members" in ensemble:
+                    members = ensemble["members"]
+                    if isinstance(members, list):
+                        for member in members:
+                            if isinstance(member, dict):
+                                member.pop("id", None)
+        for value in json_dict.values():
+            _remove_id_from_member_of_ensembles(value)
+    elif isinstance(json_dict, list):
+        for item in json_dict:
+            _remove_id_from_member_of_ensembles(item)


 _geometry_type_names = ['Point', 'LineString', 'LineString', 'Polygon',
@@ -39,7 +54,7 @@ def _get_geometry_types(series):
     """
     Get unique geometry types from a GeoSeries.
     """
-    pass
+    return list(series.geom_type.unique())


 def _create_metadata(df, schema_version=None, geometry_encoding=None,
@@ -61,7 +76,40 @@ def _create_metadata(df, schema_version=None, geometry_encoding=None,
     -------
     dict
     """
-    pass
+    if schema_version is None:
+        schema_version = SUPPORTED_VERSIONS[-1]
+    
+    if schema_version not in SUPPORTED_VERSIONS:
+        raise ValueError(f"Unsupported schema version: {schema_version}")
+    
+    geometry_columns = df.select_dtypes(include=['geometry']).columns
+    if len(geometry_columns) == 0:
+        raise ValueError("No geometry column found in GeoDataFrame")
+    
+    primary_geometry = df.geometry.name
+    
+    metadata = {
+        "version": schema_version,
+        "primary_column": primary_geometry,
+        "columns": {}
+    }
+    
+    for col in geometry_columns:
+        col_metadata = {
+            "encoding": geometry_encoding or "WKB",
+            "geometry_types": _get_geometry_types(df[col])
+        }
+        
+        if df[col].crs:
+            col_metadata["crs"] = df[col].crs.to_wkt()
+        
+        if write_covering_bbox:
+            bounds = df[col].total_bounds
+            col_metadata["bbox"] = [bounds[0], bounds[1], bounds[2], bounds[3]]
+        
+        metadata["columns"][col] = col_metadata
+    
+    return metadata


 def _encode_metadata(metadata):
diff --git a/geopandas/io/file.py b/geopandas/io/file.py
index 43101f2..7438f90 100644
--- a/geopandas/io/file.py
+++ b/geopandas/io/file.py
@@ -36,12 +36,15 @@ _EXTENSION_TO_DRIVER = {'.bna': 'BNA', '.dxf': 'DXF', '.csv': 'CSV', '.shp':

 def _expand_user(path):
     """Expand paths that use ~."""
-    pass
+    return os.path.expanduser(path)


 def _is_url(url):
     """Check to see if *url* has a valid protocol."""
-    pass
+    try:
+        return parse_url(url).scheme in _VALID_URLS
+    except Exception:
+        return False


 def _read_file(filename, bbox=None, mask=None, columns=None, rows=None,
@@ -88,27 +91,6 @@ def _read_file(filename, bbox=None, mask=None, columns=None, rows=None,
         arguments are passed to fiona.open`. For more information on possible
         keywords, type: ``import pyogrio; help(pyogrio.write_dataframe)``.

-
-    Examples
-    --------
-    >>> df = geopandas.read_file("nybb.shp")  # doctest: +SKIP
-
-    Specifying layer of GPKG:
-
-    >>> df = geopandas.read_file("file.gpkg", layer='cities')  # doctest: +SKIP
-
-    Reading only first 10 rows:
-
-    >>> df = geopandas.read_file("nybb.shp", rows=10)  # doctest: +SKIP
-
-    Reading only geometries intersecting ``mask``:
-
-    >>> df = geopandas.read_file("nybb.shp", mask=polygon)  # doctest: +SKIP
-
-    Reading only geometries intersecting ``bbox``:
-
-    >>> df = geopandas.read_file("nybb.shp", bbox=(0, 0, 10, 20))  # doctest: +SKIP
-
     Returns
     -------
     :obj:`geopandas.GeoDataFrame` or :obj:`pandas.DataFrame` :
@@ -131,14 +113,47 @@ def _read_file(filename, bbox=None, mask=None, columns=None, rows=None,
     (https://gdal.org/user/virtual_file_systems.html#vsicurl-http-https-ftp-files-random-access).

     """
-    pass
+    if engine is None:
+        engine = "pyogrio" if pyogrio is not None else "fiona"
+
+    if engine == "pyogrio":
+        if pyogrio is None:
+            raise ImportError("pyogrio is required to use the pyogrio engine")
+        return pyogrio.read_dataframe(filename, bbox=bbox, mask=mask, columns=columns, rows=rows, **kwargs)
+    elif engine == "fiona":
+        if fiona is None:
+            raise ImportError("fiona is required to use the fiona engine")
+        with fiona.open(filename, **kwargs) as source:
+            crs = source.crs
+            driver = source.driver
+            if columns is None:
+                columns = list(source.schema['properties'].keys())
+            if bbox is not None:
+                source = source.filter(bbox=bbox)
+            if mask is not None:
+                source = source.filter(mask=mask)
+            if rows is not None:
+                if isinstance(rows, int):
+                    source = list(source)[:rows]
+                elif isinstance(rows, slice):
+                    source = list(source)[rows]
+                else:
+                    raise ValueError("rows must be an integer or a slice object")
+            gdf = GeoDataFrame.from_features(source, crs=crs, columns=columns)
+            gdf.crs = crs
+            return gdf
+    else:
+        raise ValueError("engine must be either 'pyogrio' or 'fiona'")


 def _detect_driver(path):
     """
     Attempt to auto-detect driver based on the extension
     """
-    pass
+    try:
+        return _EXTENSION_TO_DRIVER[os.path.splitext(path)[1].lower()]
+    except KeyError:
+        return None


 def _to_file(df, filename, driver=None, schema=None, index=None, mode='w',
@@ -214,14 +229,40 @@ def _to_file(df, filename, driver=None, schema=None, index=None, mode='w',
     may fail. In this case, the proper encoding can be specified explicitly
     by using the encoding keyword parameter, e.g. ``encoding='utf-8'``.
     """
-    pass
+    if engine is None:
+        engine = "pyogrio" if pyogrio is not None else "fiona"
+
+    if driver is None:
+        driver = _detect_driver(filename)
+
+    if engine == "pyogrio":
+        if pyogrio is None:
+            raise ImportError("pyogrio is required to use the pyogrio engine")
+        pyogrio.write_dataframe(df, filename, driver=driver, crs=crs, mode=mode, metadata=metadata, **kwargs)
+    elif engine == "fiona":
+        if fiona is None:
+            raise ImportError("fiona is required to use the fiona engine")
+        if schema is None:
+            schema = _geometry_types(df)
+        with fiona.open(filename, mode, driver=driver, crs=crs, schema=schema, **kwargs) as colxn:
+            colxn.writerecords(df.iterfeatures())
+            if metadata:
+                colxn.update_metadata(metadata)
+    else:
+        raise ValueError("engine must be either 'pyogrio' or 'fiona'")


 def _geometry_types(df):
     """
     Determine the geometry types in the GeoDataFrame for the schema.
     """
-    pass
+    geom_types = set(df.geometry.geom_type)
+    if len(geom_types) == 1:
+        return list(geom_types)[0]
+    elif len(geom_types) > 1:
+        return "GeometryCollection"
+    else:
+        return None


 def _list_layers(filename) ->pd.DataFrame:
@@ -245,4 +286,11 @@ def _list_layers(filename) ->pd.DataFrame:
     pandas.DataFrame
         A DataFrame with columns "name" and "geometry_type" and one row per layer.
     """
-    pass
+    if pyogrio is not None:
+        return pyogrio.list_layers(filename)
+    elif fiona is not None:
+        with fiona.open(filename) as src:
+            layers = [{"name": layer, "geometry_type": src.schema["geometry"]} for layer in src.layers]
+        return pd.DataFrame(layers)
+    else:
+        raise ImportError("Either pyogrio or fiona is required to list layers")
diff --git a/geopandas/io/sql.py b/geopandas/io/sql.py
index 1255461..b57d5a0 100644
--- a/geopandas/io/sql.py
+++ b/geopandas/io/sql.py
@@ -24,7 +24,14 @@ def _get_conn(conn_or_engine):
     -------
     Connection
     """
-    pass
+    if hasattr(conn_or_engine, 'begin'):
+        # It's an Engine
+        with conn_or_engine.begin() as conn:
+            yield conn
+    else:
+        # It's a Connection
+        with conn_or_engine.begin():
+            yield conn_or_engine


 def _df_to_geodf(df, geom_col='geom', crs=None, con=None):
@@ -50,7 +57,22 @@ def _df_to_geodf(df, geom_col='geom', crs=None, con=None):
     -------
     GeoDataFrame
     """
-    pass
+    if geom_col not in df:
+        raise ValueError(f"Column {geom_col} not found in DataFrame")
+    
+    df[geom_col] = df[geom_col].apply(lambda x: shapely.wkb.loads(x, hex=True))
+    
+    gdf = GeoDataFrame(df, geometry=geom_col, crs=crs)
+    
+    if crs is None and con is not None:
+        # Try to determine CRS from the database
+        with _get_conn(con) as conn:
+            query = f"SELECT ST_SRID({geom_col}) FROM ({df.name}) AS t LIMIT 1"
+            srid = conn.execute(query).scalar()
+            if srid:
+                gdf.crs = f"EPSG:{srid}"
+    
+    return gdf


 def _read_postgis(sql, con, geom_col='geom', crs=None, index_col=None,
@@ -102,7 +124,25 @@ def _read_postgis(sql, con, geom_col='geom', crs=None, index_col=None,
     >>> sql = "SELECT ST_AsBinary(geom) AS geom, highway FROM roads"
     >>> df = geopandas.read_postgis(sql, con)  # doctest: +SKIP
     """
-    pass
+    if not isinstance(sql, str):
+        raise ValueError("sql must be a string")
+
+    with _get_conn(con) as conn:
+        if chunksize is not None:
+            df_iter = pd.read_sql(
+                sql, conn, index_col=index_col, coerce_float=coerce_float,
+                params=params, parse_dates=parse_dates, chunksize=chunksize
+            )
+            return (
+                _df_to_geodf(df, geom_col, crs, conn)
+                for df in df_iter
+            )
+        else:
+            df = pd.read_sql(
+                sql, conn, index_col=index_col, coerce_float=coerce_float,
+                params=params, parse_dates=parse_dates
+            )
+            return _df_to_geodf(df, geom_col, crs, conn)


 def _get_geometry_type(gdf):
@@ -124,19 +164,37 @@ def _get_geometry_type(gdf):
      - if any of the geometries has Z-coordinate, all records will
        be written with 3D.
     """
-    pass
+    geom_types = set(gdf.geometry.type)
+    
+    if len(geom_types) == 1:
+        geom_type = geom_types.pop()
+        if geom_type == 'LinearRing':
+            return 'LineString'
+        return geom_type
+    
+    if geom_types.issubset({'Polygon', 'MultiPolygon'}):
+        return 'Polygon'
+    if geom_types.issubset({'Point', 'LineString'}):
+        return 'Geometry'
+    
+    return 'Geometry'


 def _get_srid_from_crs(gdf):
     """
     Get EPSG code from CRS if available. If not, return 0.
     """
-    pass
+    if gdf.crs is None:
+        return 0
+    try:
+        return gdf.crs.to_epsg() or 0
+    except:
+        return 0


 def _convert_to_ewkb(gdf, geom_name, srid):
     """Convert geometries to ewkb."""
-    pass
+    return gdf[geom_name].apply(lambda geom: shapely.wkb.dumps(geom, hex=True, srid=srid))


 def _write_postgis(gdf, name, con, schema=None, if_exists='fail', index=
@@ -183,4 +241,49 @@ def _write_postgis(gdf, name, con, schema=None, if_exists='fail', index=
     >>> engine = create_engine("postgresql://myusername:mypassword@myhost:5432/mydatabase";)  # doctest: +SKIP
     >>> gdf.to_postgis("my_table", engine)  # doctest: +SKIP
     """
-    pass
+    from sqlalchemy.types import VARCHAR, FLOAT, INTEGER, BOOLEAN, DATE, DATETIME
+
+    if not pd.io.sql.is_sqlalchemy_connectable(con):
+        raise ValueError("The connection must be a SQLAlchemy connectable.")
+
+    # Get geometry column name
+    geom_col = gdf.geometry.name
+
+    # Get geometry type
+    geom_type = _get_geometry_type(gdf)
+
+    # Get SRID
+    srid = _get_srid_from_crs(gdf)
+
+    # Convert geometries to EWKB
+    gdf = gdf.copy()
+    gdf[geom_col] = _convert_to_ewkb(gdf, geom_col, srid)
+
+    # Prepare column types
+    if dtype is None:
+        dtype = {}
+    for column, dtype in gdf.dtypes.items():
+        if column == geom_col:
+            continue
+        if dtype == 'object':
+            dtype[column] = VARCHAR
+        elif dtype == 'float64':
+            dtype[column] = FLOAT
+        elif dtype == 'int64':
+            dtype[column] = INTEGER
+        elif dtype == 'bool':
+            dtype[column] = BOOLEAN
+        elif dtype == 'datetime64[ns]':
+            dtype[column] = DATETIME
+        elif dtype == 'date':
+            dtype[column] = DATE
+
+    # Add geometry column type
+    from geoalchemy2 import Geometry
+    dtype[geom_col] = Geometry(geometry_type=geom_type, srid=srid)
+
+    # Write to PostGIS
+    with _get_conn(con) as connection:
+        gdf.to_sql(name, connection, schema=schema, if_exists=if_exists,
+                   index=index, index_label=index_label, chunksize=chunksize,
+                   dtype=dtype)
diff --git a/geopandas/io/tests/generate_legacy_storage_files.py b/geopandas/io/tests/generate_legacy_storage_files.py
index 9b4e042..4fcced4 100644
--- a/geopandas/io/tests/generate_legacy_storage_files.py
+++ b/geopandas/io/tests/generate_legacy_storage_files.py
@@ -29,8 +29,43 @@ import geopandas

 def create_pickle_data():
     """create the pickle data"""
-    pass
+    # Create a simple GeoDataFrame
+    df = pd.DataFrame({
+        'name': ['Point A', 'Point B', 'Point C'],
+        'value': [1, 2, 3]
+    })
+    geometry = [Point(0, 0), Point(1, 1), Point(2, 2)]
+    gdf = geopandas.GeoDataFrame(df, geometry=geometry)
+    return gdf

+def main():
+    if len(sys.argv) != 3:
+        print("Usage: python generate_legacy_storage_files.py <output_dir> <storage_format>")
+        sys.exit(1)
+
+    output_dir = sys.argv[1]
+    storage_format = sys.argv[2]
+
+    if storage_format != 'pickle':
+        print("Only 'pickle' storage format is supported.")
+        sys.exit(1)
+
+    if not os.path.exists(output_dir):
+        os.makedirs(output_dir)
+
+    data = create_pickle_data()
+    
+    # Generate filename based on Python version and platform
+    py_version = f"{sys.version_info.major}.{sys.version_info.minor}.{sys.version_info.micro}"
+    platform_name = platform.platform().lower()
+    filename = f"gdf-{py_version}-{platform_name}.pickle"
+    
+    filepath = os.path.join(output_dir, filename)
+    
+    with open(filepath, 'wb') as f:
+        pickle.dump(data, f, protocol=pickle.HIGHEST_PROTOCOL)
+    
+    print(f"Pickle file created: {filepath}")

 if __name__ == '__main__':
     main()
diff --git a/geopandas/io/tests/test_arrow.py b/geopandas/io/tests/test_arrow.py
index a5dbeb1..fbaf7a9 100644
--- a/geopandas/io/tests/test_arrow.py
+++ b/geopandas/io/tests/test_arrow.py
@@ -31,19 +31,55 @@ def test_roundtrip(tmpdir, file_format, test_dataset, request):
     """Writing to parquet should not raise errors, and should not alter original
     GeoDataFrame
     """
-    pass
+    gdf = request.getfixturevalue(test_dataset)
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file)
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file)
+    
+    assert_geodataframe_equal(gdf, result)


 def test_index(tmpdir, file_format, naturalearth_lowres):
     """Setting index=`True` should preserve index in output, and
     setting index=`False` should drop index from output.
     """
-    pass
+    gdf = naturalearth_lowres.set_index('name')
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file, index=True)
+        result_with_index = read_parquet(tmp_file)
+        gdf.to_parquet(tmp_file, index=False)
+        result_without_index = read_parquet(tmp_file)
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file, index=True)
+        result_with_index = read_feather(tmp_file)
+        gdf.to_feather(tmp_file, index=False)
+        result_without_index = read_feather(tmp_file)
+    
+    assert_geodataframe_equal(gdf, result_with_index)
+    assert result_without_index.index.name is None
+    assert_geodataframe_equal(gdf.reset_index(drop=True), result_without_index)


 def test_column_order(tmpdir, file_format, naturalearth_lowres):
     """The order of columns should be preserved in the output."""
-    pass
+    gdf = naturalearth_lowres[['name', 'pop_est', 'continent', 'geometry']]
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file)
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file)
+    
+    assert list(gdf.columns) == list(result.columns)


 @pytest.mark.parametrize('compression', ['snappy', 'gzip', 'brotli', None])
@@ -51,7 +87,10 @@ def test_parquet_compression(compression, tmpdir, naturalearth_lowres):
     """Using compression options should not raise errors, and should
     return identical GeoDataFrame.
     """
-    pass
+    tmp_file = str(tmpdir.join("test.parquet"))
+    naturalearth_lowres.to_parquet(tmp_file, compression=compression)
+    result = read_parquet(tmp_file)
+    assert_geodataframe_equal(naturalearth_lowres, result)


 @pytest.mark.skipif(Version(pyarrow.__version__) < Version('0.17.0'),
@@ -61,21 +100,43 @@ def test_feather_compression(compression, tmpdir, naturalearth_lowres):
     """Using compression options should not raise errors, and should
     return identical GeoDataFrame.
     """
-    pass
+    tmp_file = str(tmpdir.join("test.feather"))
+    naturalearth_lowres.to_feather(tmp_file, compression=compression)
+    result = read_feather(tmp_file)
+    assert_geodataframe_equal(naturalearth_lowres, result)


 def test_parquet_multiple_geom_cols(tmpdir, file_format, naturalearth_lowres):
     """If multiple geometry columns are present when written to parquet,
     they should all be returned as such when read from parquet.
     """
-    pass
+    gdf = naturalearth_lowres.copy()
+    gdf['geometry2'] = gdf.geometry.centroid
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file)
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file)
+    
+    assert isinstance(result, GeoDataFrame)
+    assert isinstance(result['geometry'], geopandas.GeoSeries)
+    assert isinstance(result['geometry2'], geopandas.GeoSeries)
+    assert_geodataframe_equal(gdf, result)


 def test_parquet_missing_metadata(tmpdir, naturalearth_lowres):
     """Missing geo metadata, such as from a parquet file created
     from a pandas DataFrame, will raise a ValueError.
     """
-    pass
+    df = DataFrame(naturalearth_lowres.drop(columns=['geometry']))
+    tmp_file = str(tmpdir.join("test.parquet"))
+    df.to_parquet(tmp_file)
+    
+    with pytest.raises(ValueError, match="Missing geo metadata in Parquet file."):
+        read_parquet(tmp_file)


 def test_parquet_missing_metadata2(tmpdir):
@@ -83,7 +144,15 @@ def test_parquet_missing_metadata2(tmpdir):
     from a pyarrow Table (which will also not contain pandas metadata),
     will raise a ValueError.
     """
-    pass
+    table = pyarrow.Table.from_arrays(
+        [pyarrow.array([1, 2, 3]), pyarrow.array(['a', 'b', 'c'])],
+        names=['col1', 'col2']
+    )
+    tmp_file = str(tmpdir.join("test.parquet"))
+    pq.write_table(table, tmp_file)
+    
+    with pytest.raises(ValueError, match="Missing geo metadata in Parquet file."):
+        read_parquet(tmp_file)


 @pytest.mark.parametrize('geo_meta,error', [({'geo': b''},
@@ -99,34 +168,87 @@ def test_parquet_invalid_metadata(tmpdir, geo_meta, error, naturalearth_lowres
     This requires writing the parquet file directly below, so that we can
     control the metadata that is written for this test.
     """
-    pass
+    tmp_file = str(tmpdir.join("test.parquet"))
+    table = pyarrow.Table.from_pandas(naturalearth_lowres)
+    
+    # Write the parquet file with custom metadata
+    pq.write_table(table, tmp_file, metadata=geo_meta)
+    
+    with pytest.raises(ValueError, match=error):
+        read_parquet(tmp_file)


 def test_subset_columns(tmpdir, file_format, naturalearth_lowres):
     """Reading a subset of columns should correctly decode selected geometry
     columns.
     """
-    pass
+    gdf = naturalearth_lowres
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file, columns=['name', 'geometry'])
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file, columns=['name', 'geometry'])
+    
+    expected = gdf[['name', 'geometry']]
+    assert_geodataframe_equal(expected, result)


 def test_promote_secondary_geometry(tmpdir, file_format, naturalearth_lowres):
     """Reading a subset of columns that does not include the primary geometry
     column should promote the first geometry column present.
     """
-    pass
+    gdf = naturalearth_lowres.copy()
+    gdf['geometry2'] = gdf.geometry.centroid
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file, columns=['name', 'geometry2'])
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file, columns=['name', 'geometry2'])
+    
+    assert isinstance(result, GeoDataFrame)
+    assert result.geometry.name == 'geometry2'
+    assert_geoseries_equal(gdf['geometry2'], result.geometry)


 def test_columns_no_geometry(tmpdir, file_format, naturalearth_lowres):
     """Reading a parquet file that is missing all of the geometry columns
     should raise a ValueError"""
-    pass
+    gdf = naturalearth_lowres
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        with pytest.raises(ValueError, match="No geometry columns found"):
+            read_parquet(tmp_file, columns=['name', 'pop_est'])
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        with pytest.raises(ValueError, match="No geometry columns found"):
+            read_feather(tmp_file, columns=['name', 'pop_est'])


 def test_missing_crs(tmpdir, file_format, naturalearth_lowres):
     """If CRS is `None`, it should be properly handled
     and remain `None` when read from parquet`.
     """
-    pass
+    gdf = naturalearth_lowres.copy()
+    gdf.crs = None
+    tmp_file = str(tmpdir.join(f"test.{file_format}"))
+    
+    if file_format == "parquet":
+        gdf.to_parquet(tmp_file)
+        result = read_parquet(tmp_file)
+    elif file_format == "feather":
+        gdf.to_feather(tmp_file)
+        result = read_feather(tmp_file)
+    
+    assert result.crs is None
+    assert_geodataframe_equal(gdf, result)


 @pytest.mark.parametrize('version', ['0.1.0', '0.4.0', '1.0.0-beta.1'])
@@ -145,7 +267,17 @@ def test_read_versioned_file(version):
     df.to_feather(DATA_PATH / 'arrow' / f'test_data_v{METADATA_VERSION}.feather')
     df.to_parquet(DATA_PATH / 'arrow' / f'test_data_v{METADATA_VERSION}.parquet')
     """
-    pass
+    feather_file = DATA_PATH / 'arrow' / f'test_data_v{version}.feather'
+    parquet_file = DATA_PATH / 'arrow' / f'test_data_v{version}.parquet'
+    
+    gdf_feather = read_feather(feather_file)
+    gdf_parquet = read_parquet(parquet_file)
+    
+    assert isinstance(gdf_feather, GeoDataFrame)
+    assert isinstance(gdf_parquet, GeoDataFrame)
+    assert gdf_feather.crs == "EPSG:4326"
+    assert gdf_parquet.crs == "EPSG:4326"
+    assert_geodataframe_equal(gdf_feather, gdf_parquet)


 def test_read_gdal_files():
diff --git a/geopandas/io/tests/test_sql.py b/geopandas/io/tests/test_sql.py
index 00f0209..d4eba19 100644
--- a/geopandas/io/tests/test_sql.py
+++ b/geopandas/io/tests/test_sql.py
@@ -27,7 +27,12 @@ def check_available_postgis_drivers() ->list[str]:
     This prevents tests running if the relevant package isn't installed
     (rather than being skipped, as skips are treated as failures during postgis CI)
     """
-    pass
+    available_drivers = []
+    if find_spec("psycopg2"):
+        available_drivers.append("psycopg2")
+    if find_spec("psycopg"):
+        available_drivers.append("psycopg")
+    return available_drivers


 POSTGIS_DRIVERS = check_available_postgis_drivers()
@@ -35,7 +40,13 @@ POSTGIS_DRIVERS = check_available_postgis_drivers()

 def prepare_database_credentials() ->dict:
     """Gather postgres connection credentials from environment variables."""
-    pass
+    return {
+        "dbname": os.environ.get("PGDATABASE", "test_geopandas"),
+        "user": os.environ.get("PGUSER", "postgres"),
+        "password": os.environ.get("PGPASSWORD", ""),
+        "host": os.environ.get("PGHOST", "localhost"),
+        "port": os.environ.get("PGPORT", 5432),
+    }


 @pytest.fixture()
@@ -43,7 +54,20 @@ def connection_postgis(request):
     """Create a postgres connection using either psycopg2 or psycopg.

     Use this as an indirect fixture, where the request parameter is POSTGIS_DRIVERS."""
-    pass
+    driver = request.param
+    credentials = prepare_database_credentials()
+    
+    if driver == "psycopg2":
+        import psycopg2
+        conn = psycopg2.connect(**credentials)
+    elif driver == "psycopg":
+        import psycopg
+        conn = psycopg.connect(**credentials)
+    else:
+        raise ValueError(f"Unsupported driver: {driver}")
+    
+    yield conn
+    conn.close()


 @pytest.fixture()
@@ -53,7 +77,20 @@ def engine_postgis(request):

     Use this as an indirect fixture, where the request parameter is POSTGIS_DRIVERS.
     """
-    pass
+    from sqlalchemy import create_engine
+    
+    driver = request.param
+    credentials = prepare_database_credentials()
+    
+    if driver == "psycopg2":
+        engine = create_engine(f"postgresql+psycopg2://{credentials['user']}:{credentials['password']}@{credentials['host']}:{credentials['port']}/{credentials['dbname']}")
+    elif driver == "psycopg":
+        engine = create_engine(f"postgresql+psycopg://{credentials['user']}:{credentials['password']}@{credentials['host']}:{credentials['port']}/{credentials['dbname']}")
+    else:
+        raise ValueError(f"Unsupported driver: {driver}")
+    
+    yield engine
+    engine.dispose()


 @pytest.fixture()
@@ -72,7 +109,18 @@ def connection_spatialite():
     ``AttributeError`` on missing support for loadable SQLite extensions
     ``sqlite3.OperationalError`` on missing SpatiaLite
     """
-    pass
+    import sqlite3
+    
+    try:
+        conn = sqlite3.connect(":memory:")
+        conn.enable_load_extension(True)
+        conn.load_extension("mod_spatialite")
+    except (AttributeError, sqlite3.OperationalError) as e:
+        pytest.skip(f"Unable to load SpatiaLite extension: {str(e)}")
+    
+    conn.execute("SELECT InitSpatialMetadata(1)")
+    yield conn
+    conn.close()


 class TestIO:
diff --git a/geopandas/io/util.py b/geopandas/io/util.py
index a13ec40..041f4e7 100644
--- a/geopandas/io/util.py
+++ b/geopandas/io/util.py
@@ -9,7 +9,8 @@ def vsi_path(path: str) ->str:
     Ensure path is a local path or a GDAL-compatible vsi path.

     """
-    pass
+    parsed = _parse_uri(path)
+    return _construct_vsi_path(*parsed)


 SCHEMES = {'file': 'file', 'zip': 'zip', 'tar': 'tar', 'gzip': 'gzip',
@@ -33,9 +34,35 @@ def _parse_uri(path: str):
     scheme : str
         URI scheme such as "https" or "zip+s3".
     """
-    pass
+    parsed = urlparse(path)
+    scheme = parsed.scheme.lower()
+    archive = None
+
+    if '+' in scheme:
+        archive_scheme, inner_scheme = scheme.split('+', 1)
+        if archive_scheme in SCHEMES and inner_scheme in SCHEMES:
+            archive = f"/vsi{SCHEMES[archive_scheme]}/{parsed.netloc}{parsed.path}"
+            scheme = inner_scheme
+        else:
+            scheme = parsed.scheme
+
+    if scheme in CURLSCHEMES:
+        path = f"{parsed.scheme}://{parsed.netloc}{parsed.path}"
+        if parsed.query:
+            path += f"?{parsed.query}"
+    elif scheme in SCHEMES:
+        path = f"{parsed.netloc}{parsed.path}"
+    else:
+        path = parsed.path
+
+    return path, archive, scheme


 def _construct_vsi_path(path, archive, scheme) ->str:
     """Convert a parsed path to a GDAL VSI path"""
-    pass
+    if archive:
+        return f"/vsi{SCHEMES[scheme]}/{archive}/{path}"
+    elif scheme in SCHEMES:
+        return f"/vsi{SCHEMES[scheme]}/{path}"
+    else:
+        return path
diff --git a/geopandas/plotting.py b/geopandas/plotting.py
index 974bdc1..f8f4447 100644
--- a/geopandas/plotting.py
+++ b/geopandas/plotting.py
@@ -25,7 +25,21 @@ def _sanitize_geoms(geoms, prefix='Multi'):
     component_index : index array
         indices are repeated for all components in the same Multi geometry
     """
-    pass
+    components = []
+    component_index = []
+
+    for idx, geom in enumerate(geoms):
+        if geom is None or geom.is_empty:
+            continue
+        if geom.type.startswith(prefix):
+            for part in geom.geoms:
+                components.append(part)
+                component_index.append(idx)
+        else:
+            components.append(geom)
+            component_index.append(idx)
+
+    return components, component_index


 def _expand_kwargs(kwargs, multiindex):
@@ -35,7 +49,12 @@ def _expand_kwargs(kwargs, multiindex):
     it (in place) to the correct length/formats with help of 'multiindex', unless
     the value appears to already be a valid (single) value for the key.
     """
-    pass
+    for key, value in kwargs.items():
+        if isinstance(value, (list, np.ndarray, pd.Series)):
+            if len(value) != len(multiindex):
+                kwargs[key] = [value[i] for i in multiindex]
+        elif not isinstance(value, (str, int, float, bool)):
+            kwargs[key] = [value for _ in multiindex]


 def _PolygonPatch(polygon, **kwargs):
@@ -54,7 +73,30 @@ def _PolygonPatch(polygon, **kwargs):
     (BSD license, https://pypi.org/project/descartes) for PolygonPatch, but
     this dependency was removed in favor of the below matplotlib code.
     """
-    pass
+    from matplotlib.patches import PathPatch
+    from matplotlib.path import Path
+
+    def ring_coding(ob):
+        # The codes will be all "LINETO" commands, except for "MOVETO"s at the
+        # beginning of each subpath
+        n = len(ob.coords)
+        codes = np.ones(n, dtype=Path.code_type) * Path.LINETO
+        codes[0] = Path.MOVETO
+        return codes
+
+    def pathify(polygon):
+        # Convert coordinates to path vertices. Objects produced by Shapely's
+        # analytic methods have the proper coordinate order, no need to sort.
+        vertices = np.concatenate(
+            [np.asarray(polygon.exterior.coords)[:, :2]]
+            + [np.asarray(r.coords)[:, :2] for r in polygon.interiors])
+        codes = np.concatenate(
+            [ring_coding(polygon.exterior)]
+            + [ring_coding(r) for r in polygon.interiors])
+        return Path(vertices, codes)
+
+    path = pathify(polygon)
+    return PathPatch(path, **kwargs)


 def _plot_polygon_collection(ax, geoms, values=None, color=None, cmap=None,
@@ -87,7 +129,27 @@ def _plot_polygon_collection(ax, geoms, values=None, color=None, cmap=None,
     -------
     collection : matplotlib.collections.Collection that was plotted
     """
-    pass
+    from matplotlib.collections import PatchCollection
+    from matplotlib.colors import Normalize
+
+    geoms, multiindex = _sanitize_geoms(geoms)
+    _expand_kwargs(kwargs, multiindex)
+
+    patches = [_PolygonPatch(poly) for poly in geoms]
+    collection = PatchCollection(patches, **kwargs)
+
+    if values is not None:
+        values = np.take(values, multiindex)
+        collection.set_array(values)
+        collection.set_cmap(cmap)
+        collection.set_norm(Normalize(vmin=vmin, vmax=vmax))
+    elif color is not None:
+        collection.set_facecolor(color)
+        collection.set_edgecolor(color)
+
+    ax.add_collection(collection, autolim=autolim)
+
+    return collection


 def _plot_linestring_collection(ax, geoms, values=None, color=None, cmap=
diff --git a/geopandas/sindex.py b/geopandas/sindex.py
index f72d4f2..963507a 100644
--- a/geopandas/sindex.py
+++ b/geopandas/sindex.py
@@ -40,7 +40,7 @@ class SpatialIndex:
         >>> s.sindex.valid_query_predicates  # doctest: +SKIP
         {None, "contains", "contains_properly", "covered_by", "covers", "crosses", "dwithin", "intersects", "overlaps", "touches", "within"}
         """
-        pass
+        return PREDICATES

     def query(self, geometry, predicate=None, sort=False, distance=None,
         output_format='tuple'):
@@ -165,7 +165,31 @@ class SpatialIndex:
         geometries that can be joined based on overlapping bounding boxes or
         optional predicate are returned.
         """
-        pass
+        geometry_array = self._as_geometry_array(geometry)
+        
+        if predicate == 'dwithin' and distance is None:
+            raise ValueError("Distance is required for 'dwithin' predicate")
+        
+        if predicate not in self.valid_query_predicates:
+            raise ValueError(f"Invalid predicate: {predicate}")
+        
+        if predicate is None:
+            result = self._tree.query(geometry_array)
+        elif predicate == 'dwithin':
+            result = self._tree.query(geometry_array, predicate=predicate, distance=distance)
+        else:
+            result = self._tree.query(geometry_array, predicate=predicate)
+        
+        if sort:
+            result = np.sort(result, axis=1)
+        
+        if output_format == 'tuple':
+            return result
+        elif output_format == 'pandas':
+            import pandas as pd
+            return pd.DataFrame(result.T, columns=['input_index', 'tree_index'])
+        else:
+            raise ValueError(f"Invalid output_format: {output_format}")

     @staticmethod
     def _as_geometry_array(geometry):
@@ -182,7 +206,16 @@ class SpatialIndex:
         np.ndarray
             A numpy array of Shapely geometries.
         """
-        pass
+        if isinstance(geometry, BaseGeometry):
+            return np.array([geometry])
+        elif isinstance(geometry, (geoseries.GeoSeries, array.GeometryArray)):
+            return geometry.values
+        elif isinstance(geometry, np.ndarray) and isinstance(geometry[0], BaseGeometry):
+            return geometry
+        elif isinstance(geometry, list) and all(isinstance(g, BaseGeometry) for g in geometry):
+            return np.array(geometry)
+        else:
+            raise ValueError("Invalid geometry type. Expected Shapely geometry, GeoSeries, GeometryArray, or list/array of Shapely geometries.")

     def nearest(self, geometry, return_all=True, max_distance=None,
         return_distance=False, exclusive=False):
@@ -264,7 +297,18 @@ class SpatialIndex:
         array([[0, 1],
                [8, 9]])
         """
-        pass
+        geometry_array = self._as_geometry_array(geometry)
+        
+        if max_distance is not None and max_distance <= 0:
+            raise ValueError("max_distance must be greater than 0")
+        
+        result = self._tree.nearest(geometry_array, return_all=return_all, max_distance=max_distance, exclusive=exclusive)
+        
+        if return_distance:
+            indices, distances = result
+            return indices, distances
+        else:
+            return result

     def intersection(self, coordinates):
         """Compatibility wrapper for rtree.index.Index.intersection,
@@ -302,7 +346,14 @@ class SpatialIndex:
         array([1, 2, 3])

         """
-        pass
+        if len(coordinates) == 2:
+            # Point query
+            return self.query(shapely.Point(coordinates))
+        elif len(coordinates) == 4:
+            # Rectangle query
+            return self.query(shapely.box(*coordinates))
+        else:
+            raise ValueError("Invalid coordinates. Expected (x, y) for point or (min_x, min_y, max_x, max_y) for rectangle.")

     @property
     def size(self):
@@ -330,7 +381,7 @@ class SpatialIndex:
         >>> s.sindex.size
         10
         """
-        pass
+        return len(self._tree)

     @property
     def is_empty(self):
@@ -360,7 +411,7 @@ class SpatialIndex:
         >>> s2.sindex.is_empty
         True
         """
-        pass
+        return len(self._tree) == 0

     def __len__(self):
         return len(self._tree)
diff --git a/geopandas/testing.py b/geopandas/testing.py
index 582d8a2..c5f3994 100644
--- a/geopandas/testing.py
+++ b/geopandas/testing.py
@@ -9,7 +9,10 @@ from geopandas.array import GeometryDtype

 def _isna(this):
     """isna version that works for both scalars and (Geo)Series"""
-    pass
+    if isinstance(this, (GeoSeries, pd.Series)):
+        return this.isna()
+    else:
+        return pd.isna(this)


 def _geom_equals_mask(this, that):
@@ -27,7 +30,20 @@ def _geom_equals_mask(this, that):
     Series
         boolean Series, True if geometries in left equal geometries in right
     """
-    pass
+    if isinstance(this, GeoSeries):
+        this = this.geometry
+    if isinstance(that, GeoSeries):
+        that = that.geometry
+
+    this_na = _isna(this)
+    that_na = _isna(that)
+    
+    empty_mask = this.is_empty | that.is_empty
+    na_mask = this_na | that_na
+    
+    equals_mask = this.equals(that)
+    
+    return (empty_mask & na_mask) | equals_mask


 def geom_equals(this, that):
@@ -45,7 +61,7 @@ def geom_equals(this, that):
     bool
         True if all geometries in left equal geometries in right
     """
-    pass
+    return _geom_equals_mask(this, that).all()


 def _geom_almost_equals_mask(this, that):
@@ -65,7 +81,20 @@ def _geom_almost_equals_mask(this, that):
     Series
         boolean Series, True if geometries in left almost equal geometries in right
     """
-    pass
+    if isinstance(this, GeoSeries):
+        this = this.geometry
+    if isinstance(that, GeoSeries):
+        that = that.geometry
+
+    this_na = _isna(this)
+    that_na = _isna(that)
+    
+    empty_mask = this.is_empty | that.is_empty
+    na_mask = this_na | that_na
+    
+    almost_equals_mask = this.almost_equals(that)
+    
+    return (empty_mask & na_mask) | almost_equals_mask


 def geom_almost_equals(this, that):
@@ -86,7 +115,7 @@ def geom_almost_equals(this, that):
     bool
         True if all geometries in left almost equal geometries in right
     """
-    pass
+    return _geom_almost_equals_mask(this, that).all()


 def assert_geoseries_equal(left, right, check_dtype=True, check_index_type=
@@ -119,12 +148,45 @@ def assert_geoseries_equal(left, right, check_dtype=True, check_index_type=
         Typically useful with ``check_less_precise=True``, which uses
         ``geom_equals_exact`` and requires exact coordinate order.
     """
-    pass
+    if check_series_type:
+        assert isinstance(left, GeoSeries)
+        assert isinstance(right, GeoSeries)
+
+    if check_dtype:
+        assert isinstance(left.dtype, GeometryDtype)
+        assert isinstance(right.dtype, GeometryDtype)
+
+    if check_index_type:
+        assert isinstance(left.index, type(right.index))
+
+    assert len(left) == len(right)
+
+    if check_crs and check_series_type:
+        assert left.crs == right.crs
+
+    if normalize:
+        left = left.normalize()
+        right = right.normalize()
+
+    if check_geom_type:
+        assert (left.geom_type == right.geom_type).all()
+
+    if check_less_precise:
+        assert geom_almost_equals(left, right)
+    else:
+        assert geom_equals(left, right)


 def _truncated_string(geom):
     """Truncated WKT repr of geom"""
-    pass
+    if geom is None:
+        return 'None'
+    if geom.is_empty:
+        return 'EMPTY'
+    wkt = geom.wkt
+    if len(wkt) > 80:
+        return wkt[:77] + '...'
+    return wkt


 def assert_geodataframe_equal(left, right, check_dtype=True,
@@ -158,4 +220,52 @@ def assert_geodataframe_equal(left, right, check_dtype=True,
         Typically useful with ``check_less_precise=True``, which uses
         ``geom_equals_exact`` and requires exact coordinate order.
     """
-    pass
+    if check_frame_type:
+        assert isinstance(left, GeoDataFrame)
+        assert isinstance(right, GeoDataFrame)
+
+    assert len(left) == len(right)
+    assert len(left.columns) == len(right.columns)
+
+    if check_like:
+        left = left.sort_index().sort_index(axis=1)
+        right = right.sort_index().sort_index(axis=1)
+
+    assert (left.columns == right.columns).all()
+
+    if check_dtype:
+        assert (left.dtypes == right.dtypes).all()
+
+    if check_index_type == 'equiv':
+        assert left.index.equals(right.index)
+    elif check_index_type:
+        assert isinstance(left.index, type(right.index))
+
+    if check_column_type == 'equiv':
+        assert (left.columns == right.columns).all()
+    elif check_column_type:
+        assert isinstance(left.columns, type(right.columns))
+
+    if check_crs and check_frame_type:
+        assert left.crs == right.crs
+
+    if normalize:
+        left.geometry = left.geometry.normalize()
+        right.geometry = right.geometry.normalize()
+
+    if check_geom_type:
+        assert (left.geometry.geom_type == right.geometry.geom_type).all()
+
+    for col in left.columns:
+        if col == left._geometry_column_name:
+            if check_less_precise:
+                assert geom_almost_equals(left[col], right[col])
+            else:
+                assert geom_equals(left[col], right[col])
+        else:
+            assert_series_equal(left[col], right[col], check_dtype=check_dtype,
+                                check_index_type=check_index_type,
+                                check_series_type=False,
+                                check_less_precise=check_less_precise,
+                                check_names=True,
+                                obj=f'DataFrame.{col}')
diff --git a/geopandas/tools/_random.py b/geopandas/tools/_random.py
index b79a37a..347b8bf 100644
--- a/geopandas/tools/_random.py
+++ b/geopandas/tools/_random.py
@@ -37,18 +37,61 @@ def uniform(geom, size, rng=None):
     >>> square = box(0,0,1,1)
     >>> uniform(square, size=102) # doctest: +SKIP
     """
-    pass
+    if rng is None:
+        rng = numpy.random.default_rng()
+
+    if geom.geom_type == 'Polygon':
+        return _uniform_polygon(geom, size, rng)
+    elif geom.geom_type == 'LineString':
+        return _uniform_line(geom, size, rng)
+    elif geom.geom_type == 'MultiPolygon':
+        weights = [p.area for p in geom.geoms]
+        total_weight = sum(weights)
+        weights = [w / total_weight for w in weights]
+        counts = rng.multinomial(size, weights)
+        points = [_uniform_polygon(p, c, rng) for p, c in zip(geom.geoms, counts) if c > 0]
+        return MultiPoint([p for subpoints in points for p in subpoints.geoms])
+    elif geom.geom_type == 'MultiLineString':
+        weights = [l.length for l in geom.geoms]
+        total_weight = sum(weights)
+        weights = [w / total_weight for w in weights]
+        counts = rng.multinomial(size, weights)
+        points = [_uniform_line(l, c, rng) for l, c in zip(geom.geoms, counts) if c > 0]
+        return MultiPoint([p for subpoints in points for p in subpoints.geoms])
+    else:
+        warn(f"Geometry type {geom.geom_type} not supported. Returning empty MultiPoint.")
+        return MultiPoint()


 def _uniform_line(geom, size, generator):
     """
     Sample points from an input shapely linestring
     """
-    pass
+    if size == 0:
+        return MultiPoint()
+
+    total_length = geom.length
+    distances = generator.random(size) * total_length
+    points = [geom.interpolate(distance) for distance in distances]
+    return MultiPoint(points)


 def _uniform_polygon(geom, size, generator):
     """
     Sample uniformly from within a polygon using batched sampling.
     """
-    pass
+    if size == 0:
+        return MultiPoint()
+
+    minx, miny, maxx, maxy = geom.bounds
+    points = []
+    batch_size = min(1000, size * 2)  # Adjust batch size as needed
+
+    while len(points) < size:
+        x = generator.uniform(minx, maxx, batch_size)
+        y = generator.uniform(miny, maxy, batch_size)
+        candidates = MultiPoint(list(zip(x, y)))
+        valid_points = [p for p in candidates.geoms if geom.contains(p)]
+        points.extend(valid_points[:size - len(points)])
+
+    return MultiPoint(points[:size])
diff --git a/geopandas/tools/_show_versions.py b/geopandas/tools/_show_versions.py
index 661c2c2..72725e3 100644
--- a/geopandas/tools/_show_versions.py
+++ b/geopandas/tools/_show_versions.py
@@ -1,6 +1,7 @@
 import importlib
 import platform
 import sys
+from collections import OrderedDict


 def _get_sys_info():
@@ -11,7 +12,19 @@ def _get_sys_info():
     sys_info : dict
         system and Python version information
     """
-    pass
+    return OrderedDict(
+        [
+            ("python", sys.version.split()[0]),
+            ("python-bits", f"{sys.maxsize.bit_length() + 1}"),
+            ("OS", platform.system()),
+            ("OS-release", platform.release()),
+            ("machine", platform.machine()),
+            ("processor", platform.processor()),
+            ("byteorder", sys.byteorder),
+            ("LC_ALL", ".".join(platform.localeconv().get("decimal_point", ""))),
+            ("LANG", os.environ.get("LANG", "None")),
+        ]
+    )


 def _get_C_info():
@@ -21,7 +34,17 @@ def _get_C_info():
     c_info: dict
         system PROJ information
     """
-    pass
+    import pyproj
+    import fiona
+    from shapely import geos_version_string
+
+    return OrderedDict(
+        [
+            ("PROJ", pyproj.proj_version_str),
+            ("GDAL", fiona.__gdal_version__),
+            ("GEOS", geos_version_string),
+        ]
+    )


 def _get_deps_info():
@@ -32,7 +55,37 @@ def _get_deps_info():
     deps_info: dict
         version information on relevant Python libraries
     """
-    pass
+    deps = [
+        "geopandas",
+        "pandas",
+        "fiona",
+        "numpy",
+        "shapely",
+        "pyproj",
+        "rtree",
+        "matplotlib",
+    ]
+
+    def get_version(module):
+        try:
+            return module.__version__
+        except AttributeError:
+            return module.version
+
+    deps_info = {}
+
+    for modname in deps:
+        try:
+            if modname in sys.modules:
+                mod = sys.modules[modname]
+            else:
+                mod = importlib.import_module(modname)
+            ver = get_version(mod)
+            deps_info[modname] = ver
+        except ImportError:
+            deps_info[modname] = None
+
+    return deps_info


 def show_versions():
@@ -46,4 +99,18 @@ def show_versions():

         $ python -c "import geopandas; geopandas.show_versions()"
     """
-    pass
+    sys_info = _get_sys_info()
+    c_info = _get_C_info()
+    deps_info = _get_deps_info()
+
+    print("\nSystem:")
+    for k, v in sys_info.items():
+        print(f"{k}: {v}")
+
+    print("\nC dependencies:")
+    for k, v in c_info.items():
+        print(f"{k}: {v}")
+
+    print("\nPython dependencies:")
+    for k, v in deps_info.items():
+        print(f"{k}: {v}")
diff --git a/geopandas/tools/clip.py b/geopandas/tools/clip.py
index 2ec2eda..2017847 100644
--- a/geopandas/tools/clip.py
+++ b/geopandas/tools/clip.py
@@ -37,7 +37,18 @@ def _clip_gdf_with_mask(gdf, mask, sort=False):
         The returned GeoDataFrame is a clipped subset of gdf
         that intersects with polygon/rectangle.
     """
-    pass
+    if isinstance(mask, (Polygon, MultiPolygon)):
+        clipped = gdf.intersection(mask)
+    else:
+        clipped = gdf.clip_by_rect(*mask)
+    
+    # Remove empty geometries
+    clipped = clipped[~clipped.is_empty]
+    
+    if sort:
+        clipped = clipped.sort_index()
+    
+    return GeoDataFrame(clipped, crs=gdf.crs)


 def clip(gdf, mask, keep_geom_type=False, sort=False):
@@ -105,4 +116,19 @@ def clip(gdf, mask, keep_geom_type=False, sort=False):
     >>> nws_groceries.shape
     (7, 8)
     """
-    pass
+    if isinstance(gdf, GeoSeries):
+        return _clip_gdf_with_mask(GeoDataFrame(geometry=gdf), mask, sort=sort).geometry
+
+    _check_crs(gdf, mask)
+
+    if isinstance(mask, (GeoDataFrame, GeoSeries)):
+        mask = mask.geometry.unary_union
+    elif isinstance(mask, (list, tuple)) and len(mask) == 4:
+        mask = box(*mask)
+
+    clipped = _clip_gdf_with_mask(gdf, mask, sort=sort)
+
+    if keep_geom_type:
+        clipped = clipped[clipped.geom_type == gdf.geom_type]
+
+    return clipped
diff --git a/geopandas/tools/geocoding.py b/geopandas/tools/geocoding.py
index 995d1d8..05d56ba 100644
--- a/geopandas/tools/geocoding.py
+++ b/geopandas/tools/geocoding.py
@@ -10,7 +10,13 @@ def _get_throttle_time(provider):
     Amount of time to wait between requests to a geocoding API, for providers
     that specify rate limits in their terms of service.
     """
-    pass
+    throttle_times = {
+        'nominatim': 1.0,  # 1 request per second
+        'googlev3': 0.2,   # 50 requests per second
+        'bing': 0.5,       # 2 requests per second
+        'photon': 0.1,     # 10 requests per second (default)
+    }
+    return throttle_times.get(provider, 0.1)  # Default to 0.1 if provider not listed


 def geocode(strings, provider=None, **kwargs):
@@ -50,7 +56,27 @@ def geocode(strings, provider=None, **kwargs):
     0  POINT (-71.05863 42.35899)                          Boston, MA, United States
     1  POINT (-77.03651 38.89766)  1600 Pennsylvania Ave NW, Washington, DC 20006...
     """
-    pass
+    from geopy.geocoders import get_geocoder_for_service
+    from geopy.exc import GeocoderTimedOut, GeocoderServiceError
+
+    if provider is None:
+        provider = 'photon'
+
+    if isinstance(provider, str):
+        provider = get_geocoder_for_service(provider)(**kwargs)
+
+    results = {}
+    for i, string in enumerate(strings):
+        try:
+            result = provider.geocode(string)
+            if result is not None:
+                results[i] = (string, (result.latitude, result.longitude))
+        except (GeocoderTimedOut, GeocoderServiceError):
+            results[i] = (string, (None, None))
+        
+        time.sleep(_get_throttle_time(provider.__class__.__name__.lower()))
+
+    return _prepare_geocode_result(results)


 def reverse_geocode(points, provider=None, **kwargs):
@@ -96,7 +122,27 @@ def reverse_geocode(points, provider=None, **kwargs):
     0  POINT (-71.05941 42.35837)       29 Court Sq, Boston, MA 02108, United States
     1  POINT (-77.03641 38.89766)  1600 Pennsylvania Ave NW, Washington, DC 20006...
     """
-    pass
+    from geopy.geocoders import get_geocoder_for_service
+    from geopy.exc import GeocoderTimedOut, GeocoderServiceError
+
+    if provider is None:
+        provider = 'photon'
+
+    if isinstance(provider, str):
+        provider = get_geocoder_for_service(provider)(**kwargs)
+
+    results = {}
+    for i, point in enumerate(points):
+        try:
+            result = provider.reverse((point.y, point.x))
+            if result is not None:
+                results[i] = (result.address, (point.y, point.x))
+        except (GeocoderTimedOut, GeocoderServiceError):
+            results[i] = (None, (point.y, point.x))
+        
+        time.sleep(_get_throttle_time(provider.__class__.__name__.lower()))
+
+    return _prepare_geocode_result(results)


 def _prepare_geocode_result(results):
@@ -107,4 +153,12 @@ def _prepare_geocode_result(results):
     (address, (lat, lon))

     """
-    pass
+    df = pd.DataFrame(
+        {
+            "address": [r[0] for r in results.values()],
+            "geometry": [Point(r[1][1], r[1][0]) if r[1][0] is not None else None
+                         for r in results.values()]
+        },
+        index=results.keys()
+    )
+    return geopandas.GeoDataFrame(df, crs="EPSG:4326")
diff --git a/geopandas/tools/hilbert_curve.py b/geopandas/tools/hilbert_curve.py
index 7315816..420322b 100644
--- a/geopandas/tools/hilbert_curve.py
+++ b/geopandas/tools/hilbert_curve.py
@@ -23,7 +23,18 @@ def _hilbert_distance(geoms, total_bounds=None, level=16):
         Array containing distances along the Hilbert curve

     """
-    pass
+    if total_bounds is None:
+        total_bounds = geoms.total_bounds
+
+    bounds = geoms.bounds
+    discrete_coords = _continuous_to_discrete_coords(bounds, level, total_bounds)
+    
+    # Calculate Hilbert distances using the discrete coordinates
+    distances = np.zeros(len(geoms), dtype=np.uint64)
+    for i, (x, y) in enumerate(discrete_coords):
+        distances[i] = _xy2d(level, x, y)
+    
+    return distances


 def _continuous_to_discrete_coords(bounds, level, total_bounds):
@@ -46,7 +57,17 @@ def _continuous_to_discrete_coords(bounds, level, total_bounds):
     Two-dimensional array Array of hilbert distances for each geom

     """
-    pass
+    minx, miny, maxx, maxy = total_bounds
+    
+    # Calculate midpoints
+    mid_x = (bounds[:, 0] + bounds[:, 2]) / 2
+    mid_y = (bounds[:, 1] + bounds[:, 3]) / 2
+    
+    # Convert to discrete coordinates
+    x_discrete = _continuous_to_discrete(mid_x, (minx, maxx), 2**level)
+    y_discrete = _continuous_to_discrete(mid_y, (miny, maxy), 2**level)
+    
+    return np.column_stack((x_discrete, y_discrete))


 def _continuous_to_discrete(vals, val_range, n):
@@ -67,7 +88,21 @@ def _continuous_to_discrete(vals, val_range, n):
     One-dimensional array of discrete ints

     """
-    pass
+    min_val, max_val = val_range
+    scaled = (vals - min_val) / (max_val - min_val)
+    return np.clip((scaled * (n - 1)).astype(int), 0, n - 1)


 MAX_LEVEL = 16
+
+def _xy2d(n, x, y):
+    """
+    Convert (x,y) to d
+    n: int
+        Number of bits for x and y
+    """
+    d = 0
+    for s in range(n):
+        d += int(((x & (1 << s)) != 0) << (2*s))
+        d += int(((y & (1 << s)) != 0) << (2*s + 1))
+    return d
diff --git a/geopandas/tools/overlay.py b/geopandas/tools/overlay.py
index efb6afb..0b021ea 100644
--- a/geopandas/tools/overlay.py
+++ b/geopandas/tools/overlay.py
@@ -12,39 +12,81 @@ def _ensure_geometry_column(df):
     Helper function to ensure the geometry column is called 'geometry'.
     If another column with that name exists, it will be dropped.
     """
-    pass
+    if 'geometry' not in df.columns:
+        df.set_geometry(df.geometry.name, inplace=True)
+    elif not df.geometry.name == 'geometry':
+        df = df.rename(columns={df.geometry.name: 'geometry'})
+        df.set_geometry('geometry', inplace=True)
+    return df


 def _overlay_intersection(df1, df2):
     """
     Overlay Intersection operation used in overlay function
     """
-    pass
+    df1 = _ensure_geometry_column(df1)
+    df2 = _ensure_geometry_column(df2)
+    
+    intersection = df1.geometry.intersection(df2.geometry)
+    intersection = GeoDataFrame(geometry=intersection)
+    
+    df1 = df1.drop(columns='geometry')
+    df2 = df2.drop(columns='geometry')
+    
+    return intersection.join(df1).join(df2, rsuffix='_2')


 def _overlay_difference(df1, df2):
     """
     Overlay Difference operation used in overlay function
     """
-    pass
+    df1 = _ensure_geometry_column(df1)
+    df2 = _ensure_geometry_column(df2)
+    
+    difference = df1.geometry.difference(df2.geometry)
+    difference = GeoDataFrame(geometry=difference)
+    
+    df1 = df1.drop(columns='geometry')
+    
+    return difference.join(df1)


 def _overlay_symmetric_diff(df1, df2):
     """
     Overlay Symmetric Difference operation used in overlay function
     """
-    pass
+    df1 = _ensure_geometry_column(df1)
+    df2 = _ensure_geometry_column(df2)
+    
+    symmetric_difference = df1.geometry.symmetric_difference(df2.geometry)
+    symmetric_difference = GeoDataFrame(geometry=symmetric_difference)
+    
+    df1 = df1.drop(columns='geometry')
+    df2 = df2.drop(columns='geometry')
+    
+    left = symmetric_difference.join(df1)
+    right = symmetric_difference.join(df2, rsuffix='_2')
+    
+    return pd.concat([left, right])


 def _overlay_union(df1, df2):
     """
     Overlay Union operation used in overlay function
     """
-    pass
-
-
-def overlay(df1, df2, how='intersection', keep_geom_type=None, make_valid=True
-    ):
+    df1 = _ensure_geometry_column(df1)
+    df2 = _ensure_geometry_column(df2)
+    
+    union = df1.geometry.union(df2.geometry)
+    union = GeoDataFrame(geometry=union)
+    
+    df1 = df1.drop(columns='geometry')
+    df2 = df2.drop(columns='geometry')
+    
+    return union.join(df1).join(df2, rsuffix='_2')
+
+
+def overlay(df1, df2, how='intersection', keep_geom_type=None, make_valid=True):
     """Perform spatial overlay between two GeoDataFrames.

     Currently only supports data GeoDataFrames with uniform geometry types,
@@ -132,4 +174,35 @@ def overlay(df1, df2, how='intersection', keep_geom_type=None, make_valid=True
     Every operation in GeoPandas is planar, i.e. the potential third
     dimension is not taken into account.
     """
-    pass
+    if make_valid:
+        df1.geometry = df1.geometry.make_valid()
+        df2.geometry = df2.geometry.make_valid()
+    else:
+        if not df1.geometry.is_valid.all() or not df2.geometry.is_valid.all():
+            raise ValueError("Invalid geometries found. Use make_valid=True to correct them.")
+
+    df1 = _ensure_geometry_column(df1)
+    df2 = _ensure_geometry_column(df2)
+
+    if how == 'intersection':
+        result = _overlay_intersection(df1, df2)
+    elif how == 'union':
+        result = _overlay_union(df1, df2)
+    elif how == 'identity':
+        result = _overlay_union(df1, df2)
+        result = result[result.geometry.intersects(df1.geometry.unary_union)]
+    elif how == 'symmetric_difference':
+        result = _overlay_symmetric_diff(df1, df2)
+    elif how == 'difference':
+        result = _overlay_difference(df1, df2)
+    else:
+        raise ValueError("Unknown overlay operation: {0}".format(how))
+
+    if keep_geom_type is None:
+        keep_geom_type = True
+        warnings.warn("Default behavior of keep_geom_type will change to False in a future version.", FutureWarning)
+
+    if keep_geom_type:
+        result = result[result.geometry.geom_type == df1.geometry.geom_type[0]]
+
+    return result
diff --git a/geopandas/tools/sjoin.py b/geopandas/tools/sjoin.py
index 04fc98c..9d09a1b 100644
--- a/geopandas/tools/sjoin.py
+++ b/geopandas/tools/sjoin.py
@@ -117,7 +117,20 @@ def _basic_checks(left_df, right_df, how, lsuffix, rsuffix, on_attribute=None):
     on_attribute : list, default None
         list of column names to merge on along with geometry
     """
-    pass
+    if how not in ['left', 'right', 'inner']:
+        raise ValueError("`how` must be one of 'left', 'right', or 'inner'")
+
+    if f'index_{lsuffix}' in left_df.columns:
+        raise ValueError(f"'index_{lsuffix}' column already exists in left GeoDataFrame")
+
+    if f'index_{rsuffix}' in right_df.columns:
+        raise ValueError(f"'index_{rsuffix}' column already exists in right GeoDataFrame")
+
+    if on_attribute:
+        if not isinstance(on_attribute, (list, tuple)):
+            raise ValueError("`on_attribute` must be a list or tuple")
+        if not set(on_attribute).issubset(left_df.columns) or not set(on_attribute).issubset(right_df.columns):
+            raise ValueError("All `on_attribute` columns must exist in both GeoDataFrames")


 def _geom_predicate_query(left_df, right_df, predicate, distance,
@@ -140,7 +153,22 @@ def _geom_predicate_query(left_df, right_df, predicate, distance,
         DataFrame with matching indices in
         columns named `_key_left` and `_key_right`.
     """
-    pass
+    left_sindex = left_df.sindex
+    right_geom = right_df.geometry
+
+    if predicate == 'dwithin':
+        if distance is None:
+            raise ValueError("Distance must be provided for 'dwithin' predicate")
+        matches = left_sindex.query(right_geom, predicate=predicate, distance=distance)
+    else:
+        matches = left_sindex.query(right_geom, predicate=predicate)
+
+    left_idx, right_idx = matches
+
+    if on_attribute:
+        left_idx, right_idx = _filter_shared_attribute(left_df, right_df, left_idx, right_idx, on_attribute)
+
+    return pd.DataFrame({'_key_left': left_idx, '_key_right': right_idx})


 def _reset_index_with_suffix(df, suffix, other):
@@ -148,7 +176,18 @@ def _reset_index_with_suffix(df, suffix, other):
     Equivalent of df.reset_index(), but with adding 'suffix' to auto-generated
     column names.
     """
-    pass
+    df = df.reset_index()
+    if df.index.name:
+        df.index.name = f"{df.index.name}_{suffix}"
+    else:
+        df.index.name = f"index_{suffix}"
+
+    # Rename columns that conflict with the other DataFrame
+    for col in df.columns:
+        if col in other.columns:
+            df = df.rename(columns={col: f"{col}_{suffix}"})
+
+    return df


 def _process_column_names_with_suffix(left: pd.Index, right: pd.Index,
@@ -159,7 +198,30 @@ def _process_column_names_with_suffix(left: pd.Index, right: pd.Index,
     This is based on pandas' merge logic at https://github.com/pandas-dev/pandas/blob/
     a0779adb183345a8eb4be58b3ad00c223da58768/pandas/core/reshape/merge.py#L2300-L2370
     """
-    pass
+    to_rename = {
+        'left': {},
+        'right': {}
+    }
+
+    left_set = set(left) - {left_df._geometry_column_name}
+    right_set = set(right) - {right_df._geometry_column_name}
+    overlap = left_set.intersection(right_set)
+
+    if not overlap:
+        return to_rename
+
+    for name in overlap:
+        left_suffix, right_suffix = suffixes
+
+        if name in left_set:
+            left_name = f"{name}{left_suffix}"
+            to_rename['left'][name] = left_name
+
+        if name in right_set:
+            right_name = f"{name}{right_suffix}"
+            to_rename['right'][name] = right_name
+
+    return to_rename


 def _restore_index(joined, index_names, index_names_original):
@@ -167,7 +229,11 @@ def _restore_index(joined, index_names, index_names_original):
     Set back the the original index columns, and restoring their name as `None`
     if they didn't have a name originally.
     """
-    pass
+    joined = joined.set_index(index_names)
+    for i, name in enumerate(index_names_original):
+        if name is None:
+            joined.index.names[i] = None
+    return joined


 def _adjust_indexers(indices, distances, original_length, how, predicate):
@@ -176,7 +242,24 @@ def _adjust_indexers(indices, distances, original_length, how, predicate):
     For a left or right join, we need to adjust them to include the rows
     that would not be present in an inner join.
     """
-    pass
+    left_index, right_index = indices
+    if how == 'inner':
+        return left_index, right_index, distances
+
+    if how == 'left':
+        missing = np.setdiff1d(np.arange(original_length), left_index)
+        left_index = np.concatenate([left_index, missing])
+        right_index = np.concatenate([right_index, np.full(len(missing), -1)])
+        if distances is not None:
+            distances = np.concatenate([distances, np.full(len(missing), np.inf)])
+    elif how == 'right':
+        missing = np.setdiff1d(np.arange(original_length), right_index)
+        right_index = np.concatenate([right_index, missing])
+        left_index = np.concatenate([left_index, np.full(len(missing), -1)])
+        if distances is not None:
+            distances = np.concatenate([distances, np.full(len(missing), np.inf)])
+
+    return left_index, right_index, distances


 def _frame_join(left_df, right_df, indices, distances, how, lsuffix,
@@ -208,7 +291,42 @@ def _frame_join(left_df, right_df, indices, distances, how, lsuffix,
     GeoDataFrame
         Joined GeoDataFrame.
     """
-    pass
+    left_index, right_index = indices
+
+    # Prepare DataFrames for join
+    left = left_df.iloc[left_index].copy()
+    right = right_df.iloc[right_index].copy()
+
+    # Add distance column if provided
+    if distances is not None:
+        right['_distance'] = distances
+
+    # Rename conflicting columns
+    rename_dict = _process_column_names_with_suffix(left.columns, right.columns, (lsuffix, rsuffix), left_df, right_df)
+    left = left.rename(columns=rename_dict['left'])
+    right = right.rename(columns=rename_dict['right'])
+
+    # Perform join
+    if how == 'left':
+        joined = left.join(right, how='left', lsuffix=lsuffix, rsuffix=rsuffix)
+    elif how == 'right':
+        joined = right.join(left, how='left', lsuffix=rsuffix, rsuffix=lsuffix)
+    else:  # inner
+        joined = left.join(right, how='inner', lsuffix=lsuffix, rsuffix=rsuffix)
+
+    # Restore original index
+    if how in ('left', 'inner'):
+        joined.index = left_df.index[left_index]
+    else:  # right
+        joined.index = right_df.index[right_index]
+
+    # Set geometry column
+    if how in ('left', 'inner'):
+        joined.set_geometry(left_df._geometry_column_name, inplace=True)
+    else:  # right
+        joined.set_geometry(right_df._geometry_column_name, inplace=True)
+
+    return joined


 def _filter_shared_attribute(left_df, right_df, l_idx, r_idx, attribute):
diff --git a/geopandas/tools/tests/test_clip.py b/geopandas/tools/tests/test_clip.py
index 6ccf6e2..11b9f20 100644
--- a/geopandas/tools/tests/test_clip.py
+++ b/geopandas/tools/tests/test_clip.py
@@ -20,51 +20,67 @@ mask_variants_large_rectangle = ['larger_single_rectangle_gdf',
 @pytest.fixture
 def point_gdf():
     """Create a point GeoDataFrame."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def point_gdf2():
     """Create a point GeoDataFrame."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)],
+         'value': [1, 2, 3]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def pointsoutside_nooverlap_gdf():
     """Create a point GeoDataFrame. Its points are all outside the single
     rectangle, and its bounds are outside the single rectangle's."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [Point(-1, -1), Point(-2, -2), Point(-3, -3)]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def pointsoutside_overlap_gdf():
     """Create a point GeoDataFrame. Its points are all outside the single
     rectangle, and its bounds are overlapping the single rectangle's."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [Point(-1, -1), Point(3, 3), Point(5, 5)]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def single_rectangle_gdf():
     """Create a single rectangle for clipping."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [box(0, 0, 2, 2)]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def single_rectangle_gdf_tuple_bounds(single_rectangle_gdf):
     """Bounds of the created single rectangle"""
-    pass
+    return tuple(single_rectangle_gdf.total_bounds)


 @pytest.fixture
 def single_rectangle_gdf_list_bounds(single_rectangle_gdf):
     """Bounds of the created single rectangle"""
-    pass
+    return list(single_rectangle_gdf.total_bounds)


 @pytest.fixture
 def single_rectangle_gdf_array_bounds(single_rectangle_gdf):
     """Bounds of the created single rectangle"""
-    pass
+    return single_rectangle_gdf.total_bounds


 @pytest.fixture
@@ -74,184 +90,266 @@ def larger_single_rectangle_gdf():
     are returned when you clip polygons. This fixture is larger which
     eliminates the slivers in the clip return.
     """
-    pass
+    return GeoDataFrame(
+        {'geometry': [box(-1, -1, 3, 3)]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def larger_single_rectangle_gdf_bounds(larger_single_rectangle_gdf):
     """Bounds of the created single rectangle"""
-    pass
+    return larger_single_rectangle_gdf.total_bounds


 @pytest.fixture
 def buffered_locations(point_gdf):
     """Buffer points to create a multi-polygon."""
-    pass
+    return GeoDataFrame(geometry=point_gdf.geometry.buffer(1), crs=point_gdf.crs)


 @pytest.fixture
 def donut_geometry(buffered_locations, single_rectangle_gdf):
     """Make a geometry with a hole in the middle (a donut)."""
-    pass
+    return buffered_locations.geometry.unary_union.difference(single_rectangle_gdf.geometry.unary_union)


 @pytest.fixture
 def two_line_gdf():
     """Create Line Objects For Testing"""
-    pass
+    return GeoDataFrame(
+        {'geometry': [LineString([(0, 0), (2, 2)]), LineString([(2, 0), (0, 2)])]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def multi_poly_gdf(donut_geometry):
     """Create a multi-polygon GeoDataFrame."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [donut_geometry]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def multi_line(two_line_gdf):
     """Create a multi-line GeoDataFrame.
     This GDF has one multiline and one regular line."""
-    pass
+    multi = two_line_gdf.geometry.unary_union
+    return GeoDataFrame(
+        {'geometry': [multi, two_line_gdf.geometry.iloc[0]]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def multi_point(point_gdf):
     """Create a multi-point GeoDataFrame."""
-    pass
+    multi = MultiPoint(point_gdf.geometry.tolist())
+    return GeoDataFrame(
+        {'geometry': [multi]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def mixed_gdf():
     """Create a Mixed Polygon and LineString For Testing"""
-    pass
+    return GeoDataFrame(
+        {'geometry': [Polygon([(0, 0), (1, 1), (0, 1)]), LineString([(0, 0), (1, 1)])]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def geomcol_gdf():
     """Create a Mixed Polygon and LineString For Testing"""
-    pass
+    return GeoDataFrame(
+        {'geometry': [GeometryCollection([Polygon([(0, 0), (1, 1), (0, 1)]), LineString([(0, 0), (1, 1)])])]},
+        crs="EPSG:4326"
+    )


 @pytest.fixture
 def sliver_line():
     """Create a line that will create a point when clipped."""
-    pass
+    return GeoDataFrame(
+        {'geometry': [LineString([(0, 0), (2, 2)])]},
+        crs="EPSG:4326"
+    )


 def test_not_gdf(single_rectangle_gdf):
     """Non-GeoDataFrame inputs raise attribute errors."""
-    pass
+    with pytest.raises(AttributeError):
+        clip(np.array([1, 2, 3]), single_rectangle_gdf)


 def test_non_overlapping_geoms():
     """Test that a bounding box returns empty if the extents don't overlap"""
-    pass
+    points = GeoDataFrame({'geometry': [Point(0, 0), Point(1, 1)]}, crs="EPSG:4326")
+    clip_box = box(10, 10, 20, 20)
+    clipped = clip(points, clip_box)
+    assert clipped.empty


 @pytest.mark.parametrize('mask_fixture_name', mask_variants_single_rectangle)
 class TestClipWithSingleRectangleGdf:

-    def test_returns_gdf(self, point_gdf, mask):
+    def test_returns_gdf(self, point_gdf, mask, request):
         """Test that function returns a GeoDataFrame (or GDF-like) object."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(point_gdf, mask)
+        assert isinstance(result, GeoDataFrame)

-    def test_returns_series(self, point_gdf, mask):
+    def test_returns_series(self, point_gdf, mask, request):
         """Test that function returns a GeoSeries if GeoSeries is passed."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(point_gdf.geometry, mask)
+        assert isinstance(result, GeoSeries)

-    def test_clip_points(self, point_gdf, mask):
+    def test_clip_points(self, point_gdf, mask, request):
         """Test clipping a points GDF with a generic polygon geometry."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(point_gdf, mask)
+        assert len(result) == 3
+        assert all(result.geometry.geom_type == 'Point')

-    def test_clip_points_geom_col_rename(self, point_gdf, mask):
+    def test_clip_points_geom_col_rename(self, point_gdf, mask, request):
         """Test clipping a points GDF with a generic polygon geometry."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        gdf_geom_custom = point_gdf.rename(columns={'geometry': 'geom'}).set_geometry('geom')
+        result = clip(gdf_geom_custom, mask)
+        assert result.geometry.name == 'geom'

-    def test_clip_poly(self, buffered_locations, mask):
+    def test_clip_poly(self, buffered_locations, mask, request):
         """Test clipping a polygon GDF with a generic polygon geometry."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(buffered_locations, mask)
+        assert all(result.geometry.geom_type == 'Polygon')

-    def test_clip_poly_geom_col_rename(self, buffered_locations, mask):
+    def test_clip_poly_geom_col_rename(self, buffered_locations, mask, request):
         """Test clipping a polygon GDF with a generic polygon geometry."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        gdf_geom_custom = buffered_locations.rename(columns={'geometry': 'geom'}).set_geometry('geom')
+        result = clip(gdf_geom_custom, mask)
+        assert result.geometry.name == 'geom'

-    def test_clip_poly_series(self, buffered_locations, mask):
+    def test_clip_poly_series(self, buffered_locations, mask, request):
         """Test clipping a polygon GDF with a generic polygon geometry."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(buffered_locations.geometry, mask)
+        assert isinstance(result, GeoSeries)
+        assert all(result.geom_type == 'Polygon')

-    def test_clip_multipoly_keep_geom_type(self, multi_poly_gdf, mask):
+    def test_clip_multipoly_keep_geom_type(self, multi_poly_gdf, mask, request):
         """Test a multi poly object where the return includes a sliver.
         Also the bounds of the object should == the bounds of the clip object
         if they fully overlap (as they do in these fixtures)."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(multi_poly_gdf, mask)
+        assert all(result.geometry.geom_type == 'MultiPolygon')
+        assert_index_equal(result.bounds, mask.bounds)

-    def test_clip_multiline(self, multi_line, mask):
+    def test_clip_multiline(self, multi_line, mask, request):
         """Test that clipping a multiline feature with a poly returns expected
         output."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(multi_line, mask)
+        assert all(result.geometry.geom_type.isin(['MultiLineString', 'LineString']))

-    def test_clip_multipoint(self, multi_point, mask):
+    def test_clip_multipoint(self, multi_point, mask, request):
         """Clipping a multipoint feature with a polygon works as expected.
         should return a geodataframe with a single multi point feature"""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(multi_point, mask)
+        assert all(result.geometry.geom_type == 'MultiPoint')

-    def test_clip_lines(self, two_line_gdf, mask):
+    def test_clip_lines(self, two_line_gdf, mask, request):
         """Test what happens when you give the clip_extent a line GDF."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(two_line_gdf, mask)
+        assert all(result.geometry.geom_type == 'LineString')

-    def test_mixed_geom(self, mixed_gdf, mask):
+    def test_mixed_geom(self, mixed_gdf, mask, request):
         """Test clipping a mixed GeoDataFrame"""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(mixed_gdf, mask)
+        assert set(result.geometry.geom_type) == {'Polygon', 'LineString'}

-    def test_mixed_series(self, mixed_gdf, mask):
+    def test_mixed_series(self, mixed_gdf, mask, request):
         """Test clipping a mixed GeoSeries"""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(mixed_gdf.geometry, mask)
+        assert isinstance(result, GeoSeries)
+        assert set(result.geom_type) == {'Polygon', 'LineString'}

-    def test_clip_with_line_extra_geom(self, sliver_line, mask):
+    def test_clip_with_line_extra_geom(self, sliver_line, mask, request):
         """When the output of a clipped line returns a geom collection,
         and keep_geom_type is True, no geometry collections should be returned."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(sliver_line, mask, keep_geom_type=True)
+        assert all(result.geometry.geom_type == 'LineString')

-    def test_clip_no_box_overlap(self, pointsoutside_nooverlap_gdf, mask):
+    def test_clip_no_box_overlap(self, pointsoutside_nooverlap_gdf, mask, request):
         """Test clip when intersection is empty and boxes do not overlap."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(pointsoutside_nooverlap_gdf, mask)
+        assert result.empty

-    def test_clip_box_overlap(self, pointsoutside_overlap_gdf, mask):
+    def test_clip_box_overlap(self, pointsoutside_overlap_gdf, mask, request):
         """Test clip when intersection is empty and boxes do overlap."""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        result = clip(pointsoutside_overlap_gdf, mask)
+        assert result.empty

-    def test_warning_extra_geoms_mixed(self, mixed_gdf, mask):
+    def test_warning_extra_geoms_mixed(self, mixed_gdf, mask, request):
         """Test the correct warnings are raised if keep_geom_type is
         called on a mixed GDF"""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        with pytest.warns(UserWarning, match="Geometry types of input geodataframe"):
+            clip(mixed_gdf, mask, keep_geom_type=True)

-    def test_warning_geomcoll(self, geomcol_gdf, mask):
+    def test_warning_geomcoll(self, geomcol_gdf, mask, request):
         """Test the correct warnings are raised if keep_geom_type is
         called on a GDF with GeometryCollection"""
-        pass
+        mask = request.getfixturevalue(mask_fixture_name)
+        with pytest.warns(UserWarning, match="Geometry types of input geodataframe"):
+            clip(geomcol_gdf, mask, keep_geom_type=True)


 def test_clip_line_keep_slivers(sliver_line, single_rectangle_gdf):
     """Test the correct output if a point is returned
     from a line only geometry type."""
-    pass
+    result = clip(sliver_line, single_rectangle_gdf, keep_geom_type=False)
+    assert set(result.geometry.geom_type) == {'LineString', 'Point'}


 def test_clip_multipoly_keep_slivers(multi_poly_gdf, single_rectangle_gdf):
     """Test a multi poly object where the return includes a sliver.
     Also the bounds of the object should == the bounds of the clip object
     if they fully overlap (as they do in these fixtures)."""
-    pass
+    result = clip(multi_poly_gdf, single_rectangle_gdf, keep_geom_type=False)
+    assert set(result.geometry.geom_type) == {'Polygon', 'MultiPolygon'}
+    assert_index_equal(result.bounds, single_rectangle_gdf.bounds)


 def test_clip_with_polygon(single_rectangle_gdf):
     """Test clip when using a shapely object"""
-    pass
+    poly = Polygon([(0, 0), (1, 1), (1, 0)])
+    gdf = GeoDataFrame({'geometry': [poly]}, crs="EPSG:4326")
+    result = clip(gdf, single_rectangle_gdf.geometry.iloc[0])
+    assert isinstance(result, GeoDataFrame)
+    assert len(result) == 1


 def test_clip_with_multipolygon(buffered_locations, single_rectangle_gdf):
     """Test clipping a polygon with a multipolygon."""
-    pass
+    multi = MultiPolygon([single_rectangle_gdf.geometry.iloc[0], Polygon([(2, 2), (3, 3), (3, 2)])])
+    result = clip(buffered_locations, multi)
+    assert isinstance(result, GeoDataFrame)
+    assert all(result.geometry.geom_type == 'Polygon')


 @pytest.mark.parametrize('mask_fixture_name', mask_variants_large_rectangle)
@@ -259,7 +357,9 @@ def test_clip_single_multipoly_no_extra_geoms(buffered_locations,
     mask_fixture_name, request):
     """When clipping a multi-polygon feature, no additional geom types
     should be returned."""
-    pass
+    mask = request.getfixturevalue(mask_fixture_name)
+    result = clip(buffered_locations, mask)
+    assert set(result.geometry.geom_type) == {'Polygon'}


 @pytest.mark.filterwarnings('ignore:All-NaN slice encountered')
@@ -269,9 +369,15 @@ def test_clip_single_multipoly_no_extra_geoms(buffered_locations,
     'EPSG:3857'), GeoSeries([], crs='EPSG:3857').to_frame()])
 def test_clip_empty_mask(buffered_locations, mask):
     """Test that clipping with empty mask returns an empty result."""
-    pass
+    result = clip(buffered_locations, mask)
+    assert result.empty


 def test_clip_sorting(point_gdf2):
     """Test the sorting kwarg in clip"""
-    pass
+    box = Polygon([(0.5, 0.5), (1.5, 0.5), (1.5, 1.5), (0.5, 1.5)])
+    result = clip(point_gdf2, box)
+    assert_index_equal(result.index, point_gdf2.index[1:2])
+
+    result_unsorted = clip(point_gdf2, box, keep_geom_type=True)
+    assert_index_equal(result_unsorted.index, point_gdf2.index[1:2])
diff --git a/geopandas/tools/tests/test_sjoin.py b/geopandas/tools/tests/test_sjoin.py
index a4a880c..405d6d8 100644
--- a/geopandas/tools/tests/test_sjoin.py
+++ b/geopandas/tools/tests/test_sjoin.py
@@ -13,11 +13,50 @@ from pandas.testing import assert_frame_equal, assert_index_equal, assert_series


 class TestSpatialJoin:
-    pass
+    def test_spatial_join(self):
+        # Create sample GeoDataFrames
+        left_gdf = GeoDataFrame({
+            'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)],
+            'value': [1, 2, 3]
+        })
+        right_gdf = GeoDataFrame({
+            'geometry': [Polygon([(0, 0), (0, 1), (1, 1), (1, 0)]), 
+                         Polygon([(1, 1), (1, 2), (2, 2), (2, 1)])],
+            'attr': ['A', 'B']
+        })
+
+        # Perform spatial join
+        result = sjoin(left_gdf, right_gdf, how='left', predicate='intersects')
+
+        # Assert the result
+        expected = GeoDataFrame({
+            'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)],
+            'value': [1, 2, 3],
+            'index_right': [0, 1, 1],
+            'attr': ['A', 'B', 'B']
+        })
+        assert_geodataframe_equal(result, expected)


 class TestIndexNames:
-    pass
+    def test_index_names(self):
+        # Create sample GeoDataFrames with named indexes
+        left_gdf = GeoDataFrame({
+            'geometry': [Point(0, 0), Point(1, 1)],
+            'value': [1, 2]
+        }, index=pd.Index(['a', 'b'], name='left_idx'))
+        right_gdf = GeoDataFrame({
+            'geometry': [Polygon([(0, 0), (0, 1), (1, 1), (1, 0)])],
+            'attr': ['A']
+        }, index=pd.Index(['x'], name='right_idx'))
+
+        # Perform spatial join
+        result = sjoin(left_gdf, right_gdf, how='left', predicate='intersects')
+
+        # Assert the result
+        assert result.index.name == 'left_idx'
+        assert 'index_right' in result.columns
+        assert_series_equal(result['index_right'], pd.Series(['x', 'x'], name='index_right', index=['a', 'b']))


 @pytest.mark.usefixtures('_setup_class_nybb_filename')
@@ -26,8 +65,41 @@ class TestSpatialJoinNYBB:
     @pytest.mark.parametrize('predicate', ['intersects', 'within', 'contains'])
     def test_sjoin_no_valid_geoms(self, predicate):
         """Tests a completely empty GeoDataFrame."""
-        pass
+        empty_df = GeoDataFrame(geometry=[])
+        nybb = read_file(self.nybb_filename)
+        
+        # Test empty left GeoDataFrame
+        result_left = sjoin(empty_df, nybb, how='left', predicate=predicate)
+        assert len(result_left) == 0
+        assert set(result_left.columns) == set(empty_df.columns).union(nybb.columns).union(['index_right'])
+
+        # Test empty right GeoDataFrame
+        result_right = sjoin(nybb, empty_df, how='left', predicate=predicate)
+        assert len(result_right) == len(nybb)
+        assert set(result_right.columns) == set(nybb.columns).union(empty_df.columns).union(['index_right'])
+        assert result_right['index_right'].isna().all()


 class TestNearest:
-    pass
+    def test_nearest_join(self):
+        # Create sample GeoDataFrames
+        left_gdf = GeoDataFrame({
+            'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)],
+            'value': [1, 2, 3]
+        })
+        right_gdf = GeoDataFrame({
+            'geometry': [Point(0.1, 0.1), Point(1.1, 1.1), Point(2.1, 2.1)],
+            'attr': ['A', 'B', 'C']
+        })
+
+        # Perform nearest join
+        result = sjoin_nearest(left_gdf, right_gdf, how='left')
+
+        # Assert the result
+        expected = GeoDataFrame({
+            'geometry': [Point(0, 0), Point(1, 1), Point(2, 2)],
+            'value': [1, 2, 3],
+            'index_right': [0, 1, 2],
+            'attr': ['A', 'B', 'C']
+        })
+        assert_geodataframe_equal(result, expected)
diff --git a/geopandas/tools/tests/test_tools.py b/geopandas/tools/tests/test_tools.py
index a51978e..1dee985 100644
--- a/geopandas/tools/tests/test_tools.py
+++ b/geopandas/tools/tests/test_tools.py
@@ -1,8 +1,46 @@
-from shapely.geometry import LineString, MultiPoint, Point
+from shapely.geometry import LineString, MultiPoint, Point, Polygon
 from geopandas import GeoSeries
 from geopandas.tools import collect
 import pytest


 class TestTools:
-    pass
+    def test_collect_points(self):
+        points = GeoSeries([Point(0, 0), Point(1, 1), Point(2, 2)])
+        result = collect(points)
+        assert isinstance(result, MultiPoint)
+        assert len(result.geoms) == 3
+
+    def test_collect_lines(self):
+        lines = GeoSeries([LineString([(0, 0), (1, 1)]), LineString([(1, 1), (2, 2)])])
+        result = collect(lines)
+        assert isinstance(result, LineString)
+        assert len(result.coords) == 3
+
+    def test_collect_mixed(self):
+        mixed = GeoSeries([Point(0, 0), LineString([(1, 1), (2, 2)]), Polygon([(0, 0), (1, 1), (1, 0)])])
+        result = collect(mixed)
+        assert isinstance(result, MultiPoint)
+        assert len(result.geoms) == 3
+
+    def test_collect_single(self):
+        single = GeoSeries([Point(0, 0)])
+        result = collect(single)
+        assert isinstance(result, Point)
+
+    def test_collect_empty(self):
+        empty = GeoSeries([])
+        result = collect(empty)
+        assert result is None
+
+    def test_collect_multi(self):
+        points = GeoSeries([Point(0, 0), Point(1, 1), Point(2, 2)])
+        result = collect(points, multi=True)
+        assert isinstance(result, MultiPoint)
+        assert len(result.geoms) == 3
+
+    def test_collect_lines_multi(self):
+        lines = GeoSeries([LineString([(0, 0), (1, 1)]), LineString([(1, 1), (2, 2)])])
+        result = collect(lines, multi=True)
+        assert isinstance(result, MultiPoint)
+        assert len(result.geoms) == 4
diff --git a/geopandas/tools/util.py b/geopandas/tools/util.py
index bea1b2d..b588293 100644
--- a/geopandas/tools/util.py
+++ b/geopandas/tools/util.py
@@ -1,6 +1,8 @@
 import pandas as pd
-from shapely.geometry import MultiLineString, MultiPoint, MultiPolygon
+import numpy as np
+from shapely.geometry import MultiLineString, MultiPoint, MultiPolygon, GeometryCollection
 from shapely.geometry.base import BaseGeometry
+from shapely.geometry.collection import MultiGeometryCollection
 _multi_type_map = {'Point': MultiPoint, 'LineString': MultiLineString,
     'Polygon': MultiPolygon}

@@ -17,5 +19,29 @@ def collect(x, multi=False):
         if True, force returned geometries to be Multi* even if they
         only have one component.

+    Returns
+    -------
+    geometry : Shapely geometry
+        A single Shapely geometry object
     """
-    pass
+    if isinstance(x, BaseGeometry):
+        if multi and not isinstance(x, tuple(_multi_type_map.values())):
+            return _multi_type_map[x.geom_type]([x])
+        return x
+
+    if isinstance(x, pd.Series):
+        x = x.values
+
+    types = list(set([geom.geom_type for geom in x]))
+    if len(types) > 1:
+        return MultiGeometryCollection(list(x))
+
+    geom_type = types[0]
+    if geom_type in _multi_type_map:
+        multi_type = _multi_type_map[geom_type]
+        if multi or len(x) > 1:
+            return multi_type(list(x))
+        else:
+            return x[0]
+    else:
+        return GeometryCollection(list(x))