How to use the regionmask.defined_regions.natural_earth._maybe_get_column function in regionmask

def _construct_abbrevs(geodataframe, names):
    """Construct unique abbreviations based on geodataframe.names."""
    if names is None:
        raise ValueError(
            "names is None, but should be a valid column name of"
            "geodataframe, choose from {}".format(geodataframe.columns)
        )
    abbrevs = []
    names = _maybe_get_column(geodataframe, names)
    names = names.str.replace(r"[(\[\]).]", "")
    names = names.str.replace("[/-]", " ")
    abbrevs = names.str.split(" ").map(lambda x: "".join([y[:3] for y in x]))
    abbrevs = _enumerate_duplicates(abbrevs)
    return abbrevs

_check_duplicates(numbers, "numbers")
    else:
        numbers = geodataframe.index.values
    # make sure numbers is a list
    numbers = np.array(numbers)

    if names is not None:
        names = _maybe_get_column(geodataframe, names)
        _check_missing(names, "names")
        _check_duplicates(names, "names")

    if abbrevs is not None:
        if abbrevs == "_from_name":
            abbrevs = _construct_abbrevs(geodataframe, names)
        else:
            abbrevs = _maybe_get_column(geodataframe, abbrevs)
            _check_missing(abbrevs, "abbrevs")
            _check_duplicates(abbrevs, "abbrevs")

    outlines = geodataframe["geometry"]

    return Regions(
        outlines,
        numbers=numbers,
        names=names,
        abbrevs=abbrevs,
        name=name,
        source=source,
    )

if not isinstance(geodataframe, (GeoDataFrame)):
        raise TypeError("`geodataframe` must be a geopandas 'GeoDataFrame'")

    if numbers is not None:
        # sort, otherwise breaks
        geodataframe = geodataframe.sort_values(numbers)
        numbers = _maybe_get_column(geodataframe, numbers)
        _check_missing(numbers, "numbers")
        _check_duplicates(numbers, "numbers")
    else:
        numbers = geodataframe.index.values
    # make sure numbers is a list
    numbers = np.array(numbers)

    if names is not None:
        names = _maybe_get_column(geodataframe, names)
        _check_missing(names, "names")
        _check_duplicates(names, "names")

    if abbrevs is not None:
        if abbrevs == "_from_name":
            abbrevs = _construct_abbrevs(geodataframe, names)
        else:
            abbrevs = _maybe_get_column(geodataframe, abbrevs)
            _check_missing(abbrevs, "abbrevs")
            _check_duplicates(abbrevs, "abbrevs")

    outlines = geodataframe["geometry"]

    return Regions(
        outlines,
        numbers=numbers,

source of the shapefile

    Returns
    -------
    regionmask.core.regions.Regions

    """
    from geopandas import GeoDataFrame

    if not isinstance(geodataframe, (GeoDataFrame)):
        raise TypeError("`geodataframe` must be a geopandas 'GeoDataFrame'")

    if numbers is not None:
        # sort, otherwise breaks
        geodataframe = geodataframe.sort_values(numbers)
        numbers = _maybe_get_column(geodataframe, numbers)
        _check_missing(numbers, "numbers")
        _check_duplicates(numbers, "numbers")
    else:
        numbers = geodataframe.index.values
    # make sure numbers is a list
    numbers = np.array(numbers)

    if names is not None:
        names = _maybe_get_column(geodataframe, names)
        _check_missing(names, "names")
        _check_duplicates(names, "names")

    if abbrevs is not None:
        if abbrevs == "_from_name":
            abbrevs = _construct_abbrevs(geodataframe, names)
        else: