Provide links to Python source where the code is short, readable and
informative adjunct to the docs.  Forward-port of Raymond's r86225 and
r86245 using the new source reST role added in #10334.
diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index 8e97c54..58c2429 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -13,6 +13,11 @@
 or return other functions. In general, any callable object can be treated as a
 function for the purposes of this module.
 
+.. seealso::
+
+   Latest version of the :source:`functools Python source code
+   <Lib/functools.py>`
+
 The :mod:`functools` module defines the following functions:
 
 ..  function:: cmp_to_key(func)