public function attack($damage, EntityDamageEvent $source)
 {
     parent::attack($damage, $source);
     if ($source instanceof EntityDamageByEntityEvent) {
         $e = $source->getDamager();
         $deltaX = $this->x - $e->x;
         $deltaZ = $this->z - $e->z;
         $this->knockBack($e, $damage, $deltaX / 100, $deltaZ / 100, $source->getKnockBack());
     }
 }