code: func RespondWithOffense(in *dt.Msg) string {
  	for _, w := range in.Stems {
  		_, ok := offensive[w]
  		if ok {
  			return "I'm sorry, but I don't respond to rude language."
  		}
  	}
  	return ""
  }
docs: // RespondWithOffense is a one-off function to respond to rude user language by
  // refusing to process the command.