code: def _store(self, messages, response, *args, **kwargs):
          
          for storage in self.storages:
              if messages:
                  messages = storage._store(messages, response,
                      remove_oldest=False)
              # Even if there are no more messages, continue iterating to ensure
              # storages which contained messages are flushed.
              elif storage in self._used_storages:
                  storage._store([], response)
                  self._used_storages.remove(storage)
          return messages
docs: Stores the messages, returning any unstored messages after trying all
          backends.
  
          For each storage backend, any messages not stored are passed on to the
          next backend.