code: func And(left, right map[string][]string) map[string][]string {
  	result := map[string][]string{}
  	for k, v := range left {
  		result[k] = v
  	}
  
  	for k, v := range right {
  		existing, ok := result[k]
  		if ok {
  			result[k] = append(existing, v...)
  		} else {
  			result[k] = v
  		}
  	}
  
  	return result
  }
docs: // And returns a map of labels by merging the two specified values (left and right).