code: func (ls Labels) Hash() uint64 {
  	b := make([]byte, 0, 1024)
  
  	for _, v := range ls {
  		b = append(b, v.Name...)
  		b = append(b, sep)
  		b = append(b, v.Value...)
  		b = append(b, sep)
  	}
  	return xxhash.Sum64(b)
  }
docs: // Hash returns a hash value for the label set.