Intersection Makes method-types generic #51

I wish to indicate that a function of mine accepts both an "orphaned method" and a "method" of a some class. Because this is a generic method wrapper, I need it to have known param-spec and return types. For now I use:

UnwrappedClassMethod = Callable[Concatenate['Class', P], RT]
ClassMethod = Callable[P, RT]

def execute_class_method(method: Union[UnwrappedClassMethod[P, RT], ClassMethod[P,RT],
                                       *args: P.args, **kwrags: P.kwargs) -> RT: ...

What I do want is:

ClassMethod = Intersect[Callable[P, RT], MethodType]

To indicate this is both callable, and has a __func__ and __self__ attributes. Protocols can be used here, but it's and less coherent to other people.