[patrickkidger]

This is how static type checkers are told that an imported object is part of the public API for that file. (In addition to anything else present in that file.)

C.f. "the intention here is that only names imported using the form X as X will be exported" from PEP484. [1]

I'm generally a fan of the style of putting all the implementation in private modules (whose names start with an underscore) and then using __init__.py files solely to declare the public API.

[1] https://peps.python.org/pep-0484/

[tayo42]

That looks like its only for stub files not __init__.py

[patrickkidger]

It also applies to any .py file. (At least in practice with e.g. pyright)

That said, the documentation on this matter is close to nonexistent.