timm: add __all__ to __init__

[adamjstewart]

This fixes mypy errors on files like:

import timm

timm.create_model("resnet18")

The error can be reproduced using:

> mypy --strict test.py
test.py:3: error: Module "timm" does not explicitly export attribute "create_model"  [attr-defined]
Found 1 error in 1 file (checked 1 source file)

[rwightman]

Does something like __all__ = [name for name in locals() if not name.startswith('_')] keep mypy happy? because redefining everything in __init__.py in __all__ is extremely redundant and just adds to maint burden.

[adamjstewart]

Unfortunately that doesn't work for mypy, flake8, ruff, or any other static style checker as it is dynamically generated.

The maintenance burden depends on how often you update __init__ and whether or not you use tools like mypy/flake8/ruff to enforce it. FWIW, I'm willing to help maintain this myself, and can update all __init__.py files for you if you'll let me add one of the above tools to make sure it stays up to date. I would also be interested in avoiding star imports as well.