Container.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Ups\Model\Config\Source;

/**
 * Class Container
 */
class Container extends \Magento\Ups\Model\Config\Source\Generic
{
    /**
     * Carrier code
     *
     * @var string
     */
    protected $_code = 'container_description';
}