code: func (s DistinctNetSet) String() string {
  	var buf bytes.Buffer
  	buf.WriteString("{")
  	keys := make([]string, 0, len(s.members))
  	for k := range s.members {
  		keys = append(keys, k)
  	}
  	sort.Strings(keys)
  	for i, k := range keys {
  		var ip net.IP
  		if k[0] == '4' {
  			ip = make(net.IP, 4)
  		} else {
  			ip = make(net.IP, 16)
  		}
  		copy(ip, k[1:])
  		fmt.Fprintf(&buf, "%v×%d", ip, s.members[k])
  		if i != len(keys)-1 {
  			buf.WriteString(" ")
  		}
  	}
  	buf.WriteString("}")
  	return buf.String()
  }
docs: // String implements fmt.Stringer