pocketmine\event\inventory\FurnaceSmeltEvent::getSource PHP Method

    public function getSource()
    {
        return $this->source;
    }

 public function onFurnaceSmelt(FurnaceSmeltEvent $event)
 {
     $itemSkill = SkillManager::getSkillByItem($event->getSource());
     if (count($itemSkill) > 0) {
         $event->setCancelled();
     }
 }