trait SolrCommitTrait in Search API Solr 8

trait SolrCommitTrait {

  /**
   * Explicitly sends a commit command to a Solr server.
   *
   * @param \Drupal\search_api\IndexInterface $index
   *   The Search API server entity.
   *
   * @throws \Drupal\Component\Plugin\Exception\PluginException
   * @throws \Drupal\search_api\SearchApiException
   */
  protected function ensureCommit(IndexInterface $index) {
    if ($server = $index
      ->getServerInstance()) {

      /** @var \Drupal\search_api_solr\SolrBackendInterface $backend */
      $backend = $server
        ->getBackend();

      /** @var \Drupal\search_api_solr\SolrConnectorInterface $connector */
      $connector = $backend
        ->getSolrConnector();
      $update = $connector
        ->getUpdateQuery();
      $update
        ->addCommit(TRUE, TRUE, TRUE);
      $connector
        ->update($update);
      if (SOLR_INDEX_WAIT) {
        sleep(SOLR_INDEX_WAIT);
      }
    }
  }

}