Implementations of __getinitargs__ return a tuple of the positional arguments for __init__.   This wasn't initially apparent to me after reading the docs: I thought you were passing a tuple (args, kwargs) that would get called f(*args, **kwargs) and had to go to the pickle implementation to find out what you were supposed to do.

The proposed documentation enhancement: mention that you're just supposed to return a tuple of positional args and that it doesn't support kwargs.