def test_assertIsNot(self):
        """
        L{assertIsNot} passes if two objects are not identical.
        """
        a, b = MockEquality("first"), MockEquality("first")
        self.assertEqual(a, b)
        self.assertIsNot(a, b)

        L{assertIsNot} passes if two objects are not identical.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_assertions.py