prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  DOC: update read_postgis docstring for CRS changes
  The read_postgis docstring still mentions to use a dict:
  
  https://github.com/geopandas/geopandas/blob/078062d303e401aaa5e37e04c0e7c3ce188920fe/geopandas/io/sql.py#L33-L36
  
  we should update this to follow how CRS is explained in other places now we use pyproj.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `geopandas/io/sql.py`
  Content:
  ```
  1 import sys
  2 
  3 import pandas as pd
  4 
  5 import shapely.wkb
  6 
  7 from geopandas import GeoDataFrame
  8 
  9 
  10 def read_postgis(
  11     sql,
  12     con,
  13     geom_col="geom",
  14     crs=None,
  15     index_col=None,
  16     coerce_float=True,
  17     parse_dates=None,
  18     params=None,
  19 ):
  20     """
  21     Returns a GeoDataFrame corresponding to the result of the query
  22     string, which must contain a geometry column in WKB representation.
  23 
  24     Parameters
  25     ----------
  26     sql : string
  27         SQL query to execute in selecting entries from database, or name
  28         of the table to read from the database.
  29     con : DB connection object or SQLAlchemy engine
  30         Active connection to the database to query.
  31     geom_col : string, default 'geom'
  32         column name to convert to shapely geometries
  33     crs : dict or str, optional
  34         CRS to use for the returned GeoDataFrame; if not set, tries to
  35         determine CRS from the SRID associated with the first geometry in
  36         the database, and assigns that to all geometries.
  37 
  38     See the documentation for pandas.read_sql for further explanation
  39     of the following parameters:
  40     index_col, coerce_float, parse_dates, params
  41 
  42     Returns
  43     -------
  44     GeoDataFrame
  45 
  46     Example
  47     -------
  48     PostGIS
  49     >>> sql = "SELECT geom, kind FROM polygons"
  50     SpatiaLite
  51     >>> sql = "SELECT ST_AsBinary(geom) AS geom, kind FROM polygons"
  52     >>> df = geopandas.read_postgis(sql, con)
  53     """
  54 
  55     df = pd.read_sql(
  56         sql,
  57         con,
  58         index_col=index_col,
  59         coerce_float=coerce_float,
  60         parse_dates=parse_dates,
  61         params=params,
  62     )
  63 
  64     if geom_col not in df:
  65         raise ValueError("Query missing geometry column '{}'".format(geom_col))
  66 
  67     geoms = df[geom_col].dropna()
  68 
  69     if not geoms.empty:
  70         load_geom_bytes = shapely.wkb.loads
  71         """Load from Python 3 binary."""
  72 
  73         def load_geom_buffer(x):
  74             """Load from Python 2 binary."""
  75             return shapely.wkb.loads(str(x))
  76 
  77         def load_geom_text(x):
  78             """Load from binary encoded as text."""
  79             return shapely.wkb.loads(str(x), hex=True)
  80 
  81         if sys.version_info.major < 3:
  82             if isinstance(geoms.iat[0], buffer):
  83                 load_geom = load_geom_buffer
  84             else:
  85                 load_geom = load_geom_text
  86         elif isinstance(geoms.iat[0], bytes):
  87             load_geom = load_geom_bytes
  88         else:
  89             load_geom = load_geom_text
  90 
  91         df[geom_col] = geoms = geoms.apply(load_geom)
  92         if crs is None:
  93             srid = shapely.geos.lgeos.GEOSGetSRID(geoms.iat[0]._geom)
  94             # if no defined SRID in geodatabase, returns SRID of 0
  95             if srid != 0:
  96                 crs = "epsg:{}".format(srid)
  97 
  98     return GeoDataFrame(df, crs=crs, geometry=geom_col)
  99
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/geopandas/io/sql.py b/geopandas/io/sql.py
  --- a/geopandas/io/sql.py
  +++ b/geopandas/io/sql.py
  @@ -30,10 +30,12 @@
           Active connection to the database to query.
       geom_col : string, default 'geom'
           column name to convert to shapely geometries
  -    crs : dict or str, optional
  -        CRS to use for the returned GeoDataFrame; if not set, tries to
  -        determine CRS from the SRID associated with the first geometry in
  -        the database, and assigns that to all geometries.
  +    crs : pyproj.CRS, optional
  +        CRS to use for the returned GeoDataFrame. The value can be anything accepted
  +        by :meth:`pyproj.CRS.from_user_input() <pyproj.crs.CRS.from_user_input>`,
  +        such as an authority string (eg "EPSG:4326") or a WKT string.
  +        If not set, tries to determine CRS from the SRID associated with the
  +        first geometry in the database, and assigns that to all geometries.
   
       See the documentation for pandas.read_sql for further explanation
       of the following parameters:
  
verification_info: {"golden_diff": "diff --git a/geopandas/io/sql.py b/geopandas/io/sql.py\n--- a/geopandas/io/sql.py\n+++ b/geopandas/io/sql.py\n@@ -30,10 +30,12 @@\n         Active connection to the database to query.\n     geom_col : string, default 'geom'\n         column name to convert to shapely geometries\n-    crs : dict or str, optional\n-        CRS to use for the returned GeoDataFrame; if not set, tries to\n-        determine CRS from the SRID associated with the first geometry in\n-        the database, and assigns that to all geometries.\n+    crs : pyproj.CRS, optional\n+        CRS to use for the returned GeoDataFrame. The value can be anything accepted\n+        by :meth:`pyproj.CRS.from_user_input() <pyproj.crs.CRS.from_user_input>`,\n+        such as an authority string (eg \"EPSG:4326\") or a WKT string.\n+        If not set, tries to determine CRS from the SRID associated with the\n+        first geometry in the database, and assigns that to all geometries.\n \n     See the documentation for pandas.read_sql for further explanation\n     of the following parameters:\n", "issue": "DOC: update read_postgis docstring for CRS changes\nThe read_postgis docstring still mentions to use a dict:\r\n\r\nhttps://github.com/geopandas/geopandas/blob/078062d303e401aaa5e37e04c0e7c3ce188920fe/geopandas/io/sql.py#L33-L36\r\n\r\nwe should update this to follow how CRS is explained in other places now we use pyproj.\n", "before_files": [{"content": "import sys\n\nimport pandas as pd\n\nimport shapely.wkb\n\nfrom geopandas import GeoDataFrame\n\n\ndef read_postgis(\n    sql,\n    con,\n    geom_col=\"geom\",\n    crs=None,\n    index_col=None,\n    coerce_float=True,\n    parse_dates=None,\n    params=None,\n):\n    \"\"\"\n    Returns a GeoDataFrame corresponding to the result of the query\n    string, which must contain a geometry column in WKB representation.\n\n    Parameters\n    ----------\n    sql : string\n        SQL query to execute in selecting entries from database, or name\n        of the table to read from the database.\n    con : DB connection object or SQLAlchemy engine\n        Active connection to the database to query.\n    geom_col : string, default 'geom'\n        column name to convert to shapely geometries\n    crs : dict or str, optional\n        CRS to use for the returned GeoDataFrame; if not set, tries to\n        determine CRS from the SRID associated with the first geometry in\n        the database, and assigns that to all geometries.\n\n    See the documentation for pandas.read_sql for further explanation\n    of the following parameters:\n    index_col, coerce_float, parse_dates, params\n\n    Returns\n    -------\n    GeoDataFrame\n\n    Example\n    -------\n    PostGIS\n    >>> sql = \"SELECT geom, kind FROM polygons\"\n    SpatiaLite\n    >>> sql = \"SELECT ST_AsBinary(geom) AS geom, kind FROM polygons\"\n    >>> df = geopandas.read_postgis(sql, con)\n    \"\"\"\n\n    df = pd.read_sql(\n        sql,\n        con,\n        index_col=index_col,\n        coerce_float=coerce_float,\n        parse_dates=parse_dates,\n        params=params,\n    )\n\n    if geom_col not in df:\n        raise ValueError(\"Query missing geometry column '{}'\".format(geom_col))\n\n    geoms = df[geom_col].dropna()\n\n    if not geoms.empty:\n        load_geom_bytes = shapely.wkb.loads\n        \"\"\"Load from Python 3 binary.\"\"\"\n\n        def load_geom_buffer(x):\n            \"\"\"Load from Python 2 binary.\"\"\"\n            return shapely.wkb.loads(str(x))\n\n        def load_geom_text(x):\n            \"\"\"Load from binary encoded as text.\"\"\"\n            return shapely.wkb.loads(str(x), hex=True)\n\n        if sys.version_info.major < 3:\n            if isinstance(geoms.iat[0], buffer):\n                load_geom = load_geom_buffer\n            else:\n                load_geom = load_geom_text\n        elif isinstance(geoms.iat[0], bytes):\n            load_geom = load_geom_bytes\n        else:\n            load_geom = load_geom_text\n\n        df[geom_col] = geoms = geoms.apply(load_geom)\n        if crs is None:\n            srid = shapely.geos.lgeos.GEOSGetSRID(geoms.iat[0]._geom)\n            # if no defined SRID in geodatabase, returns SRID of 0\n            if srid != 0:\n                crs = \"epsg:{}\".format(srid)\n\n    return GeoDataFrame(df, crs=crs, geometry=geom_col)\n", "path": "geopandas/io/sql.py"}], "after_files": [{"content": "import sys\n\nimport pandas as pd\n\nimport shapely.wkb\n\nfrom geopandas import GeoDataFrame\n\n\ndef read_postgis(\n    sql,\n    con,\n    geom_col=\"geom\",\n    crs=None,\n    index_col=None,\n    coerce_float=True,\n    parse_dates=None,\n    params=None,\n):\n    \"\"\"\n    Returns a GeoDataFrame corresponding to the result of the query\n    string, which must contain a geometry column in WKB representation.\n\n    Parameters\n    ----------\n    sql : string\n        SQL query to execute in selecting entries from database, or name\n        of the table to read from the database.\n    con : DB connection object or SQLAlchemy engine\n        Active connection to the database to query.\n    geom_col : string, default 'geom'\n        column name to convert to shapely geometries\n    crs : pyproj.CRS, optional\n        CRS to use for the returned GeoDataFrame. The value can be anything accepted\n        by :meth:`pyproj.CRS.from_user_input() <pyproj.crs.CRS.from_user_input>`,\n        such as an authority string (eg \"EPSG:4326\") or a WKT string.\n        If not set, tries to determine CRS from the SRID associated with the\n        first geometry in the database, and assigns that to all geometries.\n\n    See the documentation for pandas.read_sql for further explanation\n    of the following parameters:\n    index_col, coerce_float, parse_dates, params\n\n    Returns\n    -------\n    GeoDataFrame\n\n    Example\n    -------\n    PostGIS\n    >>> sql = \"SELECT geom, kind FROM polygons\"\n    SpatiaLite\n    >>> sql = \"SELECT ST_AsBinary(geom) AS geom, kind FROM polygons\"\n    >>> df = geopandas.read_postgis(sql, con)\n    \"\"\"\n\n    df = pd.read_sql(\n        sql,\n        con,\n        index_col=index_col,\n        coerce_float=coerce_float,\n        parse_dates=parse_dates,\n        params=params,\n    )\n\n    if geom_col not in df:\n        raise ValueError(\"Query missing geometry column '{}'\".format(geom_col))\n\n    geoms = df[geom_col].dropna()\n\n    if not geoms.empty:\n        load_geom_bytes = shapely.wkb.loads\n        \"\"\"Load from Python 3 binary.\"\"\"\n\n        def load_geom_buffer(x):\n            \"\"\"Load from Python 2 binary.\"\"\"\n            return shapely.wkb.loads(str(x))\n\n        def load_geom_text(x):\n            \"\"\"Load from binary encoded as text.\"\"\"\n            return shapely.wkb.loads(str(x), hex=True)\n\n        if sys.version_info.major < 3:\n            if isinstance(geoms.iat[0], buffer):\n                load_geom = load_geom_buffer\n            else:\n                load_geom = load_geom_text\n        elif isinstance(geoms.iat[0], bytes):\n            load_geom = load_geom_bytes\n        else:\n            load_geom = load_geom_text\n\n        df[geom_col] = geoms = geoms.apply(load_geom)\n        if crs is None:\n            srid = shapely.geos.lgeos.GEOSGetSRID(geoms.iat[0]._geom)\n            # if no defined SRID in geodatabase, returns SRID of 0\n            if srid != 0:\n                crs = \"epsg:{}\".format(srid)\n\n    return GeoDataFrame(df, crs=crs, geometry=geom_col)\n", "path": "geopandas/io/sql.py"}]}