If module A has a small intended public API, you can structure it no matter how you want to achieve that. You can put those internal symbols behind their own object/class/module if you prefer.

Using `__all__` has one functional consequence, which is `from A import *`. Again, I would avoid * imports entirely, but if you want to try to curb possible downstream problems from users who do indeed use * imports, I would also prefer not defining `__all__` because it's extra boilerplate you have to maintain and can very easily be missed on future updates.