docs: def next(self):
          """Get the next batch of messages from the previously fetched messages.
  
          If there's no more messages, check if we should auto-delete the
          messages and raise StopIteration.
          """
          if not self._messages:
              if self.auto_delete:
                  self.delete_messages()
              raise StopIteration
  
          message = self._messages.pop(0)
          self._processed_messages.append(message)
          return json.loads(message.payload)