Add MutableSet example.

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index b136cf15041cbced317fbf17395ba278dff5774e..4e79e2512d0dfa6b556fe9ffbe4fa66816099013 100644 (file)
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -132,7 +132,12 @@ 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`.
 
 
 :class:`Counter` objects