drupal8 で パスに応じたページテンプレート名を利用する方法

テーマ名_theme_suggestions_page_alter(array &$suggestions, array $variables) {
  $current_path = \Drupal::service('path.current')->getPath();
  $alias = explode('?', $_SERVER['REQUEST_URI']);
  $alias = $alias[0];
  if ($alias) {
    $suggestion = 'page';
    $aliases = explode('/', $alias);
    array_shift($aliases);
    $suggestion .= '_';
    foreach ($aliases as $a) {
      $suggestion .= '_' . $a;
      $suggestions[] = $suggestion;
    }
  }
}