code: def create_message(payload, key=None):
      
      assert payload is None or isinstance(payload, bytes), 'payload={!r} should be bytes or None'.format(payload)
      assert key is None or isinstance(key, bytes), 'key={!r} should be bytes or None'.format(key)
      return Message(0, 0, key, payload)
docs: Construct a :class:`Message`
  
      :param payload: The payload to send to Kafka.
      :type payload: :class:`bytes` or ``None``
      :param key: A key used to route the message when partitioning and to
          determine message identity on a compacted topic.
      :type key: :class:`bytes` or ``None``