mypy with cyclic dep

main.py

import u


print(u.U().foo())

u.py

# import v


# class U(object):
#     def foo(self) -> 'U':
#         return v.V().bar(self)


from v import V


class U(object):
    def foo(self) -> 'U':
        return V().bar(self)

v.py

# import u


# class V(object):
#     def bar(self, x) -> 'u.U':
#         return x


# from u import U


class V(object):
    def bar(self, x) -> 'U':
        return x