Class Rev

Lib/test/test_collections.py:1046–1048

        self.assertIsInstance(RevPlusIter(), Reversible)
        # Check None blocking
        class Rev:
            def __iter__(self): return iter([])
            def __reversed__(self): return reversed([])
        class RevItBlocked(Rev):
            __iter__ = None
        class RevRevBlocked(Rev):