pytype: stop excluding mercurial/ui.py ui.extractchoices() is perhaps making assumptions that it shouldn't about the pattern always matching, but presumably we have test coverage for that. PyCharm flags the updated classes with a warning "Class xxx must implement all abstract methods", and suggests adding `abc.ABC` to the superclasses. I'm not sure why, unless it doesn't recognize the `__getattr__()` delegation pattern. Additionally, we can't unconditionally subclass `typing.BinaryIO` because that defeats the `__getattr__` delegation to the wrapped object at runtime. Instead, it has to only subclass during the type checking phase[1]. In any event, this fixes: File "/mnt/c/Users/Matt/hg/mercurial/ui.py", line 1518, in _runpager: Function subprocess.Popen.__new__ was called with the wrong arguments [wrong-arg-types] Expected: (cls, args, bufsize, executable, stdin, stdout: Optional[Union[IO, int]] = ..., ...) Actually passed: (cls, args, bufsize, stdin, stdout: Union[mercurial.utils.procutil.WriteAllWrapper, mercurial.windows.winstdout], ...) File "/mnt/c/Users/Matt/hg/mercurial/ui.py", line 1798, in extractchoices: No attribute 'group' on None [attribute-error] In Optional[Match[bytes]] File "/mnt/c/Users/Matt/hg/mercurial/ui.py", line 1799, in extractchoices: No attribute 'group' on None [attribute-error] In Optional[Match[bytes]] [1] https://stackoverflow.com/q/71365594