code: func (ls Labels) HashForLabels(names ...string) uint64 {
  	b := make([]byte, 0, 1024)
  
  	for _, v := range ls {
  		for _, n := range names {
  			if v.Name == n {
  				b = append(b, v.Name...)
  				b = append(b, sep)
  				b = append(b, v.Value...)
  				b = append(b, sep)
  				break
  			}
  		}
  	}
  	return xxhash.Sum64(b)
  }
docs: // HashForLabels returns a hash value for the labels matching the provided names.