code: public function load(ObjectManager $manager)
      {
          $rootNodeFr = $this->generateRootNodeFr();
          $manager->persist($rootNodeFr);
          $this->generateRouteNode($manager, $rootNodeFr);
  
          $deletedNodeFr = $this->generateDeletedNodeFr();
          $manager->persist($deletedNodeFr);
  
          $manager->flush();
      }
docs: Load data fixtures with the passed EntityManager
  
  @param ObjectManager $manager