VariantInterface

class \Drupal\Core\Display\VariantBase extends \Drupal\Core\Plugin\PluginBase implements \Drupal\Core\Display\VariantInterface uses \Drupal\Core\Plugin\PluginDependencyTrait, \Drupal\Core\Cache\RefinableCacheableDependencyTrait
class \Drupal\Core\Render\Plugin\DisplayVariant\SimplePageVariant extends \Drupal\Core\Display\VariantBase implements \Drupal\Core\Display\PageVariantInterface
class \Drupal\block\Plugin\DisplayVariant\BlockPageVariant extends \Drupal\Core\Display\VariantBase implements \Drupal\Core\Display\PageVariantInterface, \Drupal\Core\Plugin\ContainerFactoryPluginInterface