code: func Join(ss ...[]string) []string {
  	used := map[string]bool{}
  	var s []string
  	for _, tmp := range ss {
  		for _, w := range tmp {
  			if !used[w] {
  				s = append(s, w)
  			}
  			used[w] = true
  		}
  	}
  	return s
  }
docs: // Join concatenates triggers together, like Recommend() and Broken(), ensuring
  // no duplicates exist