class BlockContent

class BlockContent extends DeriverBase implements ContainerDeriverInterface {
    
    /**
     * The custom block storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $blockContentStorage;
    
    /**
     * Constructs a BlockContent object.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $block_content_storage
     *   The custom block storage.
     */
    public function __construct(EntityStorageInterface $block_content_storage) {
        $this->blockContentStorage = $block_content_storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, $base_plugin_id) {
        $entity_type_manager = $container->get('entity_type.manager');
        return new static($entity_type_manager->getStorage('block_content'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDerivativeDefinitions($base_plugin_definition) {
        $block_contents = $this->blockContentStorage
            ->loadByProperties([
            'reusable' => TRUE,
        ]);
        // Reset the discovered definitions.
        $this->derivatives = [];
        
        /** @var $block_content \Drupal\block_content\Entity\BlockContent */
        foreach ($block_contents as $block_content) {
            $this->derivatives[$block_content->uuid()] = $base_plugin_definition;
            $this->derivatives[$block_content->uuid()]['admin_label'] = $block_content->label();
            $this->derivatives[$block_content->uuid()]['config_dependencies']['content'] = [
                $block_content->getConfigDependencyName(),
            ];
        }
        return parent::getDerivativeDefinitions($base_plugin_definition);
    }

}