code: func (s *Sample) string() string {
  	ss := []string{}
  	var sv string
  	for _, v := range s.Value {
  		sv = fmt.Sprintf("%s %10d", sv, v)
  	}
  	sv = sv + ": "
  	for _, l := range s.Location {
  		sv = sv + fmt.Sprintf("%d ", l.ID)
  	}
  	ss = append(ss, sv)
  	const labelHeader = "                "
  	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")
  }
docs: // string dumps a text representation of a sample. Intended mainly
  // for debugging purposes.