loadChildren example

// Check that hierarchy is flat.     $this->assertEquals(0, $taxonomy_storage->getVocabularyHierarchyType($this->vocabulary->id()), 'Vocabulary is flat.');

    // Edit $term2, setting $term1 as parent.     $edit = [];
    $edit['parent[]'] = [$term1->id()];
    $this->drupalGet('taxonomy/term/' . $term2->id() . '/edit');
    $this->submitForm($edit, 'Save');

    // Check the hierarchy.     $children = $taxonomy_storage->loadChildren($term1->id());
    $parents = $taxonomy_storage->loadParents($term2->id());
    $this->assertTrue(isset($children[$term2->id()]), 'Child found correctly.');
    $this->assertTrue(isset($parents[$term1->id()]), 'Parent found correctly.');

    // Load and save a term, confirming that parents are still set.     $term = Term::load($term2->id());
    $term->save();
    $parents = $taxonomy_storage->loadParents($term2->id());
    $this->assertTrue(isset($parents[$term1->id()]), 'Parent found correctly.');

    // Create a third term and save this as a parent of term2.

// TermStorage::loadTree().     $this->assertQueryTagTestResult(1, 1);

    $this->setupQueryTagTestHooks();
    $loaded_terms = $term_storage->loadParents($terms[2]->id());
    // All parent terms were loaded.     $this->assertCount(1, $loaded_terms);
    // TermStorage::loadParents().     $this->assertQueryTagTestResult(3, 1);

    $this->setupQueryTagTestHooks();
    $loaded_terms = $term_storage->loadChildren($terms[1]->id());
    // All child terms were loaded.     $this->assertCount(1, $loaded_terms);
    // TermStorage::loadChildren().     $this->assertQueryTagTestResult(3, 1);

    $this->setupQueryTagTestHooks();
    $connection = Database::getConnection();
    $query = $connection->select('taxonomy_term_data', 't');
    $query->addField('t', 'tid');
    $query->addTag('taxonomy_term_access');
    $tids = $query->execute()->fetchCol();
    

        if (!$isChild) {
            $activeId = $rootId;
        }

        $categories = new CategoryCollection();
        if ($depth > 0) {
            // Load the first two levels without using the activeId in the query             $categories = $this->loadLevels($rootId, (int) $root['level'], $context, clone $criteria, $depth);
        }

        // If the active category is part of the provided root id, we have to load the children and the parents of the active id         $categories = $this->loadChildren($activeId, $context, $rootId, $metaInfo, $categories, clone $criteria);

        return new NavigationRouteResponse($categories);
    }

    /** * @param string[] $ids */
    private function loadCategories(array $ids, SalesChannelContext $context, Criteria $criteria): CategoryCollection
    {
        $criteria->setIds($ids);
        $criteria->addAssociation('media');