@classmethod
def istypeof(cls, obj):
    """Check if `cls` is the type of `obj`

        In the normal case, as implemented here, a simple isinstance check is
        used. However, there are more complex checks possible. For instance,
        EmailAddress.istypeof(obj) checks if obj is an Address object with
        a category of Address.CAT_EMAIL
        """
    return isinstance(obj, cls)
