docs: def _get(self, *args, **kwargs):
          """
          Gets a single list of messages from all storage backends.
          """
          all_messages = []
          for storage in self.storages:
              messages, all_retrieved = storage._get()
              # If the backend hasn't been used, no more retrieval is necessary.
              if messages is None:
                  break
              if messages:
                  self._used_storages.add(storage)
              all_messages.extend(messages)
              # If this storage class contained all the messages, no further
              # retrieval is necessary
              if all_retrieved:
                  break
          return all_messages, all_retrieved