if len(s.Label) > 0 {
		ss = append(ss, labelHeader+labelsToString(s.Label))
	}
	if len(s.NumLabel) > 0 {
		ss = append(ss, labelHeader+numLabelsToString(s.NumLabel, s.NumUnit))
	}
	return strings.Join(ss, "\n")
}

// labelsToString returns a string representation of a
// map representing labels.
func labelsToString(labels map[string][]string) string {
	ls := []string{}