[Typing-sig] PEP 647 (type guards) -- final call for comments

I think we have reached consensus on PEP 647 in typing-sig. We have implementations for mypy and pyright, not sure about the rest. This PEP does not affect CPython directly except for the addition of one special item (TypeGuard) to typing.py -- it would be nice to get that in the 3.10 stdlib. I'm CC'ing python-dev here to see if there are any further comments; if not, we can initiate the approval process by creating an issue at https://github.com/python/steering-council. -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>