vendor/omnipay/paypal/src/PayPalItemBag.php

<?php
namespace Omnipay\PayPal;
 
use Omnipay\Common\ItemBag;
use Omnipay\Common\ItemInterface;
 
class PayPalItemBag extends ItemBag
{
    public function add($item)
    {
        if ($item instanceof ItemInterface) {
            $this->items[] = $item;
        } else {
            $this->items[] = new PayPalItem($item);
        }
    }
}