I noticed while investigating #5750 that I got Any from a method associated as returning _typeshed.Self. I tracked down that it is because to mypy 0.910, _typeshed.Self doesn't exist yet because it's bundling an older version of the stdlib. The problem went away when I manually added Self to the installed stub file for _typeshed.

I see two options:

• Ignore the problem and wait for the next mypy release to update typeshed. Until then, people will just see Any types from anything we annotate with Self in third-party packages.
• Avoid using Self in third-party packages for now.