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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def reverse(self):
 """ Reverse the order of all items in the dictionary. Example: omd = omdict([(1,1), (1,11), (1,111), (2,2), (3,3)]) omd.reverse() omd.allitems() == [(3,3), (2,2), (1,111), (1,11), (1,1)] Returns: <self>. """

        for key in six.iterkeys(self._map):
            self._map[key].reverse()
        self._items.reverse()
        return self