import types
class Type(type):
    __class__ = property({}.__getitem__, {}.__setitem__)
class Object(metaclass=Type):
    __slots__ = '__class__'

for cls in (type, Type):
    print(isinstance(Object, cls))  # True.
for cls in (list, int, types.CodeType, types.MethodType):
    try:
        print(isinstance(Object, cls))  # KeyError: <class '__main__.Object'>
    except KeyError as err:
        print(cls.__name__, err.args[0])