Add count() method to collections.deque().
diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index 7de016f..3021f63 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -113,6 +113,13 @@
             d = deque('abc')
             d.maxlen = 10
 
+    def test_count(self):
+        for s in ('', 'abracadabra', 'simsalabim'*500+'abc'):
+            s = list(s)
+            d = deque(s)
+            for letter in 'abcdefghijklmnopqrstuvwxyz':
+                self.assertEqual(s.count(letter), d.count(letter), (s, d, letter))
+
     def test_comparisons(self):
         d = deque('xabc'); d.popleft()
         for e in [d, deque('abc'), deque('ab'), deque(), list(d)]: