code: func (f *Finder) IDFromArgs(args []string) (string, error) {
  	switch len(args) {
  	case 1:
  		return args[0], nil
  
  	case 2:
  		ixn, err := f.Find(args[0], args[1])
  		if err != nil {
  			return "", err
  		}
  		if ixn == nil {
  			return "", fmt.Errorf(
  				"Intention with source %q and destination %q not found.",
  				args[0], args[1])
  		}
  
  		return ixn.ID, nil
  
  	default:
  		return "", fmt.Errorf("command requires exactly 1 or 2 arguments")
  	}
  }
docs: // ID returns the intention ID for the given CLI args. An error is returned
  // if args is not 1 or 2 elements.