Sometimes you want to say that an argument must follow two or more different protocols. For example, you might want to state that an argument must be an Iterable and a Container (for example, it could be a Set, a Mapping or a Sequence). It would be nice if this could be spelled like this:

def assertIn(item: T, thing: Intersection[Iterable[T], Container[T]]) -> None:
    if item not in thing:
        # Debug output
        for it in thing:
            print(it)