Checking functions that accept Ellipsis arguments

[t-vi]

I have a function (__getitem__) that accepts integers or ellipsis arguments.
I haven't found a way to specify this in a stub (pyi) file so that mypy will like it.

class X:
    def __getitem__(self, idx: Union[int, ???]) -> 'X': ...

but what to write in place of ???.
One solution would be None-style Ellipsis, but that doesn't work currently.
(numpy ndarrays would have the same issue, but I haven't found a stub file for them.)

I would greatly appreciate any hint how this works and if there is a way this works, my feature request would be to add a hint in the documentation, too.

[gvanrossum]

Duplicate of #4791.

[t-vi]

Ah, sorry. Thank you for pointing to #4791.