That's a non-problem, since the user defines __call__ in the first
place. If you plan for an extension you can define your __call__ to
call '_call_' if you want; to change an existing class you can alway
derive a new class and and give it a different __call__ method...
--Guido van Rossum, CWI, Amsterdam <Guido.van.Rossum@cwi.nl>