Add MutableSet example.

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index eab4510efc0d73671c2c1e9978bf08224fc803ec..094c629b3676e3a678917d3997c61d0dc9b4d3b7 100644 (file)
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -135,7 +135,12 @@ Notes on using :class:`Set` and :class:`MutableSet` as a mixin:
    inherit from both :meth:`Set` and :meth:`Hashable`, then define
    ``__hash__ = Set._hash``.
 
-(For more about ABCs, see the :mod:`abc` module and :pep:`3119`.)
+.. seealso::
+
+   * `OrderedSet recipe <http://code.activestate.com/recipes/576694/>`_ for an
+     example built on :class:`MutableSet`.
+
+   * For more about ABCs, see the :mod:`abc` module and :pep:`3119`.
 
 
 .. _deque-objects: