PreviewFallbackInterface

class \Drupal\Core\Block\BlockBase implements \Drupal\Core\Block\BlockPluginInterface, \Drupal\Core\Plugin\PluginWithFormsInterface, \Drupal\Core\Render\PreviewFallbackInterface uses \Drupal\Core\Block\BlockPluginTrait, \Drupal\Core\Plugin\ContextAwarePluginAssignmentTrait extends \Drupal\Core\Plugin\ContextAwarePluginBase
class \Drupal\Core\Block\Plugin\Block\PageTitleBlock implements \Drupal\Core\Block\TitleBlockPluginInterface extends \Drupal\Core\Block\BlockBase
class \Drupal\Core\Menu\Plugin\Block\LocalActionsBlock implements \Drupal\Core\Plugin\ContainerFactoryPluginInterface extends \Drupal\Core\Block\BlockBase
class \Drupal\Core\Menu\Plugin\Block\LocalTasksBlock implements \Drupal\Core\Plugin\ContainerFactoryPluginInterface extends \Drupal\Core\Block\BlockBase

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