buildMediaTypeMenu example

    // to load the changed library content. This is not only more efficient, but     // also provides a more accessible user experience for screen readers.     if ($state->get('media_library_content') === '1') {
      return $this->buildLibraryContent($state);
    }
    else {
      return [
        '#theme' => 'media_library_wrapper',
        '#attributes' => [
          'id' => 'media-library-wrapper',
        ],
        'menu' => $this->buildMediaTypeMenu($state),
        'content' => $this->buildLibraryContent($state),
        // Attach the JavaScript for the media library UI. The number of         // available slots needs to be added to make sure users can't select         // more items than allowed.         '#attached' => [
          'library' => ['media_library/ui'],
          'drupalSettings' => [
            'media_library' => [
              'selection_remaining' => $state->getAvailableSlots(),
            ],
          ],
        ],