@classmethod
def __is_multivalued_dict__(cls, x):
    """
            >>> mv_d = multivalued_dict()
            >>> multivalued_dict.__is_multivalued_dict__(mv_d)
            True
        """
    return isinstance(x, cls) or ((True if x.default_factory == type([]) else
        False) if isinstance(x, cls.defaultdict) else False)
