bjects.
    register_series_accessor : Register a custom accessor on Series objects.
    register_index_accessor : Register a custom accessor on Index objects.

    Notes
    -----
    When accessed, your accessor will be initialized with the pandas object
    the user is interacting with. So the signature must be

    .. code-block:: python

        def __init__(self, pandas_object):  # noqa: E999
            ...

    For consistency with pandas methods, you should raise an ``AttributeError``
    if the data passed to your accessor has an incorrect dtype.

    >>> pd.Series(['a', 'b']).dt
    Traceback (most recent call last):
    ...
    AttributeError: Can only use .dt accessor with datetimelike values

    Examples
    --------
    In your library code::

        import pandas as pd

        @pd.api.extensions.register_dataframe_accessor("geo")
        class GeoAccessor:
            def __init__(self, pandas_obj):
                self._obj = pandas_obj

            @property
            def center(self):
                # return the geographic center point of this DataFrame
                lat = self._obj.latitude
                lon = self._obj.longitude
                return (float(lon.mean()), float(lat.mean()))

            def plot(self):
                # plot this array's data on a map, e.g., using Cartopy
                pass

    Back in an interactive IPython session:

        .. code-block:: ipython

            In [1]: ds = pd.DataFrame({{"longitude": np.linspace(0, 10),
               ...:                    "latitude": np.linspace(0, 20)}})
            In [2]: ds.geo.center
            Out[2]: (5.0, 10.0)
            In [3]: ds.geo.plot()  # plots data on a map
    c