code: func (m Map) Format() []string {
  	res := make([]string, 0, len(m))
  	for k, values := range m {
  		for _, v := range values {
  			res = append(res, Format(k, v))
  		}
  	}
  	sort.Strings(res)
  	return res
  }
docs: // Format converts m to a sorted list of strings.