Get rid of _tag->closure->_tag reference cycle

flask/sessions.py

@@ -52,13 +52,7 @@ class SessionMixin(object):
     modified = True
 
 
-class TaggedJSONSerializer(object):
-    """A customized JSON serializer that supports a few extra types that
-    we take for granted when serializing (tuples, markup objects, datetime).
-    """
-
-    def dumps(self, value):
-        def _tag(value):
+def _tag(value):
     if isinstance(value, tuple):
         return {' t': [_tag(x) for x in value]}
     elif isinstance(value, uuid.UUID):
@@ -82,6 +76,14 @@ class TaggedJSONSerializer(object):
                 u'which can only store unicode strings.  Consider '
                 u'base64 encoding your string (String was %r)' % value)
     return value
+
+
+class TaggedJSONSerializer(object):
+    """A customized JSON serializer that supports a few extra types that
+    we take for granted when serializing (tuples, markup objects, datetime).
+    """
+
+    def dumps(self, value):
         return json.dumps(_tag(value), separators=(',', ':'))
 
     def loads(self, value):