Class MMC

Lib/test/test_typing.py:7759–7769

            MMA()

        class MMC(MMA):
            def __getitem__(self, k):
                return None
            def __setitem__(self, k, v):
                pass
            def __delitem__(self, k):
                pass
            def __iter__(self):
                return iter(())
            def __len__(self):
                return 0

        self.assertEqual(len(MMC()), 0)
        self.assertTrue(callable(MMC.update))