import inspect


def get_mro(cls):
    """
    Wrapper on top of :func:`inspect.getmro` that recognizes ``None`` as a
    type (treated like ``type(None)``).
    """
    if cls is type(None) or cls is None:
        return (type(None), object)
    else:
        assert isinstance(cls, type)
        return inspect.getmro(cls)