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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 _cached(self, dbname, coll, index):
 """Test if `index` is cached."""

        cache = self.__index_cache
        now = datetime.datetime.utcnow()
        with self.__index_cache_lock:
            return (dbname in cache and
                    coll in cache[dbname] and
                    index in cache[dbname][coll] and
                    now < cache[dbname][coll][index])