Cart\Cart::has PHP Method

    public function has($itemId)
    {
        return !is_null($this->find($itemId));
    }

 /**
  * @param Cart   $cart
  * @param string $cartItemId
  * @param int    $amount
  */
 protected function handlePOSTUpdateAmount($cart, $cartItemId, $amount)
 {
     if (!$cart->has($cartItemId)) {
         return;
     }
     if ($amount === 0) {
         $cart->remove($cartItemId);
     } else {
         $cart->update($cartItemId, 'quantity', intval($amount));
     }
 }