Fatal error: Uncaught Error: Interface 'Drupal\Core\Plugin\PluginFormInterface' not found in /var/www/html/tmp/contrib/flag/src/FlagType/FlagTypePluginInterface.php:15 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/flag/src/FlagType/FlagTypePluginInterface.php on line 15