code: func getTopic(obj interface{}) (string, bool) {
  	record, ok := obj.(*goavro.Record)
  	if !ok {
  		return "UNKNOWN_RECORD_TYPE", false
  	}
  	topicObj, err := record.Get("topic")
  	if err != nil {
  		return "UNKNOWN_TOPIC_VAL", false
  	}
  	topicStr, ok := topicObj.(string)
  	if !ok {
  		return "UNKNOWN_TOPIC_TYPE", false
  	}
  	return topicStr, true
  }
docs: // getTopic returns the requested topic from an Avro record.