class ImageStyleListBuilder

class ImageStyleListBuilder extends ConfigEntityListBuilder {
  
  /**
   * {@inheritdoc}
   */
  public function buildHeader() {
    $header['label'] = $this->t('Style name');
    return $header + parent::buildHeader();
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildRow(EntityInterface $entity) {
    $row['label'] = $entity->label();
    return $row + parent::buildRow($entity);
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getDefaultOperations(EntityInterface $entity) {
    $args = func_get_args();
    $cacheability = $args[1] ?? new CacheableMetadata();
    $flush = [
      'title' => $this->t('Flush'),
      'weight' => 200,
      'url' => $entity->toUrl('flush-form'),
    ];
    return parent::getDefaultOperations($entity, $cacheability) + [
      'flush' => $flush,
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function render() {
    $build = parent::render();
    $build['table']['#empty'] = $this->t('There are currently no styles. <a href=":url">Add a new one</a>.', [
      ':url' => Url::fromRoute('image.style_add')->toString(),
    ]);
    return $build;
  }

}