>>> DummyDict = TypedDict('DummyDict', {'x': int, 'y': str}, total=False)
>>> DummyDict.__required_keys__
frozenset({'x', 'y'})

This happens because the TypedDict function does not pass the "total" metaclass argument to _TypedDictMeta() (instead passing "__total__" in the attribute namespace) and the new code that sets __required_keys__ and __optional_keys__ only checks the metaclass argument.