sendChunk example

  protected function sendPreBody($pre_body, array $no_js_placeholders, AttachedAssetsInterface $cumulative_assets) {
    // If there are no no-JS BigPipe placeholders, we can send the pre-</body>     // part of the page immediately.     if (empty($no_js_placeholders)) {
      $this->sendChunk($pre_body);
      return;
    }

    // Extract the scripts_bottom markup: the no-JS BigPipe placeholders that we     // will render may attach additional asset libraries, and if so, it will be     // necessary to re-render scripts_bottom.     [$pre_scripts_bottom, $scripts_bottom, $post_scripts_bottom] = explode('<drupal-big-pipe-scripts-bottom-marker>', $pre_body, 3);
    $cumulative_assets_initial = clone $cumulative_assets;

    $this->sendNoJsPlaceholders($pre_scripts_bottom . $post_scripts_bottom, $no_js_placeholders, $cumulative_assets);