Cara membalikkan class function berikut

Bagimana cara membalikkan class berikut :

   public static function Itemtype($itemtype = '') {
      return (!class_exists($itemtype)
              || !in_array($itemtype, self::getBlacklistItemtype()));
   }

   public static function getBlacklistItemtype() {
      return [
        'Class 1',
        'Class 2',
      ];
   }