code: func (t *Topic) marshalConfig(data map[string]string) ([]byte, error) {
  	cfg := topicConfig{Version: 1, ConfigMap: data}
  	if cfg.ConfigMap == nil {
  		cfg.ConfigMap = make(map[string]string)
  	}
  	return json.Marshal(&cfg)
  }
docs: // marshalConfig turns a config map into the json representation
  // needed for Zookeeper