typing-extensions

typing-extensionsでもtyping_extensionsでもインストールできるっぽい

The typing_extensions module serves two related purposes:

Enable use of new type system features on older Python versions.

Enable experimentation with new type system PEPs before they are accepted and added to the typing module.

typing-extensionsを見ておけば、型まわりのPythonの変更は追従できそう