Support PEP 604: Allow writing union types as X | Y

[rchen152]

PEP: https://www.python.org/dev/peps/pep-0604/

Introduces new syntax that we should support as soon as possible so typeshed can start using it (python/typeshed#4819).

[commentator8]

Hi - i see the code seems to be checking if the context is 3.10 if ctx.python_version >= (3, 10) and name == "__or__": - we are using from future import __annotations__ in python 3.9. Am i correct that it still wont work for 3.9 then?

[martindemello]

Hi @commentator8 , that's right, the feature made it into python in 3.10 so we don't support it in earlier versions, even with from future import __annotations__ or explicit string annotations.

[commentator8]

Good to know. Thanks. I've recently disabled pytype for our company's pipelines and was hoping to bring it back.