feat: add typing on some public api functions

[pbabics]

What does this pull request do?

• Adds typing on some of the publicly exposed API functions
• Explicitly export API in __init__.py

[cla-checker-service[bot]]

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[xrmx]

Thanks for the PR. We should probably add some mypy run in CI to check we are not messing up anything.

[pbabics]

Hello, I've checked mypy output and there is a lot of errors because most of the code either does not have typing or has wrong/incomplete typing

[xrmx]

Hello, I've checked mypy output and there is a lot of errors because most of the code either does not have typing or has wrong/incomplete typing

Right, maybe we can think of an incremental strategy for typing. Let me think about it a bit.