buildLibraryContent example

  public function buildUi(MediaLibraryState $state = NULL) {
    if (!$state) {
      $state = MediaLibraryState::fromRequest($this->request);
    }
    // When navigating to a media type through the vertical tabs, we only want     // 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