code: func MarshalInternalMessage(m Message, s Serializer) ([]byte, error) {
  	typ := getMessageType(m)
  	buf, err := s.Marshal(m)
  	if err != nil {
  		return nil, errors.Wrap(err, "marshaling")
  	}
  	return append([]byte{typ}, buf...), nil
  }
docs: // MarshalInternalMessage serializes the pilosa message and adds pilosa internal
  // type info which is used by the internal messaging stuff.