Constructor.
\Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher: The event dispatcher.
\Drupal\rdf\SiteSchema\SiteSchemaManager $site_schema_manager: The site schema manager.
public function __construct(EventDispatcherInterface $dispatcher, SiteSchemaManager $site_schema_manager) {
$this->dispatcher = $dispatcher;
$this->siteSchemaManager = $site_schema_manager;
}