typing: Session.__init__
typing: Session.__init__

Pulled out of https://github.com/pytest-dev/pytest/pull/6491.

nicoddemus/pytest,Akasurde/pytest,RonnyPfannschmidt/pytest,markshao/pytest,The-Compiler/pytest,pytest-dev/pytest,nicoddemus/pytest,The-Compiler/pytest,alfredodeza/pytest