bug with __ior__

[skogsbaer]

In test_interface_set.py, there is a test case test_ior that is currently being skipped.

The builtin set type seems to play some tricks on ior, which seems to return NotImplemented. I guess that a workaround would be to swap to order in the ProtocolWrapper: the methods with type annotations should not call the methods of the wrapped type, instead they should call the methods of the wrapper.