Fatal error: Uncaught Error: Class "Magento\Eav\Model\Entity\Attribute\Source\AbstractSource" not found in /var/www/magento/html/app/code/MGS/Lookbook/Model/Entity/Attribute/Backend/Lookbook.php:8 Stack trace: #0 {main} thrown in /var/www/magento/html/app/code/MGS/Lookbook/Model/Entity/Attribute/Backend/Lookbook.php on line 8