Support Python types properly

[begleynk]

Typing module: https://docs.python.org/3/library/typing.html

This task can be split into multiple tasks. E.g.

• Type aliases: https://docs.python.org/3/library/typing.html#type-aliases
• Generics: https://docs.python.org/3/library/typing.html#user-defined-generic-types
• NewType: https://docs.python.org/3/library/typing.html#newtype