pocketmine\inventory\BaseInventory::slotContains PHP Method

    public function slotContains($slot, Item $item, $matchCount = false)
    {
        if ($matchCount) {
            return $this->getItem($slot)->deepEquals($item, true, true, true);
        } else {
            return $this->getItem($slot)->deepEquals($item) and $this->getItem($slot)->getCount() >= $item->getCount();
        }
    }