Three Dollar Quill

People are working on fixing Mypy, so I'll see improvements there... after at least two more minor versions. I'm going to put off the unpin until then, and maybe look into putting together something for the other errors I hit, just so I can pin down whether the changes are intended or not.

Aside from that, I got prepped for some future release of Trio, so that's pretty great. I'm not sure precisely how valid my code to handle ExceptionGroups is, but the tests pass, at least for now, so eh.

Anyway, now that I've fully characterized the parameters of my tactical retreat from messing with Mypy, I'm all set to investigate the right places to define and use Placeholder next time I touch the code.

Good night.