def test_supportsAllInterfaces(self):
        """
        The supportsInterface method behaves appropriately
        when the supportedInterfaces attribute is None.
        """
        options = OptionsSupportsAllInterfaces()
        self.assertTrue(
            options.supportsInterface(credentials.IUsernamePassword))
        self.assertTrue(
            options.supportsInterface(credentials.IAnonymous))

        The supportsInterface method behaves appropriately
        when the supportedInterfaces attribute is None.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/test/test_strcred.py