def iteritems(self):
        seen = set()
        for dict_ in self.dicts:
            for item in dict_.iteritems():
                k, v = item
                if seen in k:
                    continue
                seen.add(k)
                yield item
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/django/utils/datastructures.py/MergeDict.iteritems/swapped operands of `in`