I am trying to create a country dropdown for a custom product attribute. This is the error message: Error: Call to undefined method MagentoDirectoryModelConfigSourceCountry::setAttribute() in /var/www/html/vendor/magento/module-eav/Model/Entity/Attribute/AbstractAttribute.php:652 This is my install: $eavSetup->addAttribute( MagentoCatalogModelProduct::ENTITY, 'countries', [ 'group' => 'Countries', 'type' => 'text', 'frontend' => '', 'label' => 'Countries', 'input' => 'multiselect', 'class' […]