code: func ExtractYesNo(s string) (bool, error) {
  	ss := strings.Fields(strings.ToLower(s))
  	for _, w := range ss {
  		w = strings.TrimRight(w, " .,;:!?'\"")
  		_, ok := yes[w]
  		if ok {
  			return true, nil
  		}
  		_, ok = no[w]
  		if ok {
  			return false, nil
  		}
  	}
  	return false, ErrNotFound
  }
docs: // ExtractYesNo determines whether a string contains a Yes or No response.
  // This is useful for plugins to determine a user's answer to a Yes/No question.