Right, there's a very similar instance-method-reuse related problem described in http://bugs.python.org/issue29270, where ctypes re-uses a class namespace is define a swapped-endianness version of the originally defined class.

The easiest place to deflect conflicts is at the point where bound instance methods are created:


>>> bound_method = MyList().insert
>>> bound_method.__self__.__class__
<class '__main__.MyList'>
>>> bound_method.__func__.__closure__[0].cell_contents
<class '__main__.MyList'>
>>> bound_method.__self__.__class__ is bound_method.__func__.__closure__[0].cell_contents
False

However, that method of detection only works for plain instance methods that only close over the `__class__` variable: as soon as you wrap them in a decorator, you may not have easy access to the `__closure__` attribute any more, and if the method has closure references to more than just `__class__`, then it's a bit more work to find the right closure index from outside the function.