I understood. The idea is that "<class 'collections.abc.Iterable'>" is subclass of "<class 'str'>" so type of "<class 'collections.abc.Iterable'>" is equel to type of "<class 'str'>" in some way(as I understood).

One test in "handle inheritance correctly" says that Test Passed when nothing is returned and the exception is not raised while the res of function is "string is one", type of res is "<class 'str'>" and expected type is "<class 'collections.abc.Iterable'>". I think in such a case it should raise UnexpectedTypeException 'cause str is not collections.abc.Iterable', but then it says that the test is not passed.

P.S. Sorry for my clumsy English