shipping-notifications/ShippingNotifications/Model/ResourceModel/ShippingCategory.php

<?php

namespace Cpcommerce\ShippingNotifications\Model\ResourceModel;

use \Magento\Framework\Model\ResourceModel\Db\AbstractDb;

class ShippingCategory extends AbstractDb
{
    protected function _construct(){
        $this->_init('cpcommerce_shipping_notification_categories', 'ship_categ_id');
    }
}