Fix typo (reported by Hiro Ashiya).
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index 0b45fe1..4975f74 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -821,10 +821,10 @@
 
           >>> d = OrderedDict.fromkeys('abcde')
           >>> d.move_to_end('b')
-          >>> ''.join(d.keys)
+          >>> ''.join(d.keys())
           'acdeb'
           >>> d.move_to_end('b', last=False)
-          >>> ''.join(d.keys)
+          >>> ''.join(d.keys())
           'bacde'
 
       .. versionadded:: 3.2