Backport 3.3 fixes and cleans ups.
diff --git a/Lib/collections.py b/Lib/collections.py
index 3693926..b904980 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -716,6 +716,9 @@
     def __contains__(self, key):
         return any(key in m for m in self.maps)
 
+    def __bool__(self):
+        return any(self.maps)
+
     @_recursive_repr()
     def __repr__(self):
         return '{0.__class__.__name__}({1})'.format(