Class CustomSet

Lib/test/test_dictviews.py:97–99

        d4 = {'d': 4}

        class CustomSet(set):
            def intersection(self, other):
                return CustomSet(super().intersection(other))

        self.assertEqual(d1.keys() & d1.keys(), {'a', 'b'})
        self.assertEqual(d1.keys() & d2.keys(), {'b'})