如何找到源collections.deque？

我需要为继承到deque的类添加功能,但更喜欢查看collections.deque中的代码来实现新的类final.

>>> from _collections import deque, defaultdict
>>> inspect.getfile(deque)
'/usr/lib/python2.7/collections.pyc'
>>> inspect.getfile(collections)
'/usr/lib/python2.7/collections.pyc'
>>> inspect.getfile(_collections)
Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/lib/python2.7/inspect.py", line 403, in getfile
    raise TypeError('{!r} is a built-in module'.format(object))
TypeError:  is a built-in module
>>> 

我在哪里可以找到collections.deque的源代码？这是源集合,但不包含collections.deque.- > http://hg.python.org/cpython/file/2.7/Lib/collections.py