Fix set representation in an example.
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index c893e22..411d5f6 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -661,7 +661,7 @@
    ...     d[k].add(v)
    ...
    >>> list(d.items())
-   [('blue', set([2, 4])), ('red', set([1, 3]))]
+   [('blue', {2, 4}), ('red', {1, 3})]
 
 
 :func:`namedtuple` Factory Function for Tuples with Named Fields