code: def find_all_by_mapreduce_state(cls, mapreduce_state):
      keys = cls.calculate_keys_by_mapreduce_state(mapreduce_state)
      i = 0
      while i < len(keys):
        @db.non_transactional
        def no_tx_get(i):
          return db.get(keys[i:i+cls._MAX_STATES_IN_MEMORY])
        states = no_tx_get(i)
        for s in states:
          i += 1
          if s is not None:
            yield s