def lower_items(self):
        return (
            (lowerkey, keyval[1])
            for (lowerkey, keyval)
            in self._store.items()
        )
MongoDB will automatically clear expired keys.
dataset/ETHPy150Open kevin1024/vcrpy/vcr/util.py/CaseInsensitiveDict.lower_items--crossover with--dataset/ETHPy150Open tweepy/tweepy/tweepy/cache.py/MongodbCache.cleanup