Add MutableSet example.

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index a860a53a7197395a9abebb87c285093ed9cb3296..4ef0ca4488ea6125edd6227dd43469a3e385af4d 100644 (file)
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -147,8 +147,12 @@ 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: