code: func AddLabel(labels map[string]string, labelKey, labelValue string) map[string]string {
  	if labelKey == "" {
  		// Don't need to add a label.
  		return labels
  	}
  	if labels == nil {
  		labels = make(map[string]string)
  	}
  	labels[labelKey] = labelValue
  	return labels
  }
docs: // AddLabel returns a map with the given key and value added to the given map.