Getting the class of a method in Python 2.2 (semantic change from 2.1)

[Kali Kim]

class A:
    def aaa(self):
        pass

class B(A):
    def bbb(self):
        pass

def whosemethod(method):
    return method.im_class.__name__

With Python 2.1,

>>> whosemethod(B.bbb)
'B'
>>> whosemethod(B.aaa)
'A'

But with Python 2.2,

>>> whosemethod(B.bbb)
'B'
>>> whosemethod(B.aaa)
'B'

I want to know where B.aaa is getting inherited from, but can't find a
*easy and obvious* (tm) way with Python 2.2.

Can anyone help me?