Add a missing docstring
diff --git a/Lib/collections.py b/Lib/collections.py
index 1dcd233..66e8a24 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -1,3 +1,15 @@
+'''This module implements specialized container datatypes providing
+alternatives to Python’s general purpose built-in containers, dict,
+list, set, and tuple.
+
+* namedtuple factory function for creating tuple subclasses with named fields
+* deque list-like container with fast appends and pops on either end
+* Counter dict subclass for counting hashable objects
+* OrderedDict dict subclass that remembers the order entries were added
+* defaultdict dict subclass that calls a factory function to supply missing values
+
+'''
+
__all__ = ['Counter', 'deque', 'defaultdict', 'namedtuple', 'OrderedDict']
# For bootstrapping reasons, the collection ABCs are defined in _abcoll.py.
# They should however be considered an integral part of collections.py.