code: private function importExampleWebsite(): ?RedirectResponse
      {
          $installTool = $this->container->get('contao.install_tool');
          $templates = $installTool->getTemplates();
  
          $this->context['templates'] = $templates;
  
          if ($installTool->getConfig('exampleWebsite')) {
              $this->context['import_date'] = date('Y-m-d H:i', $installTool->getConfig('exampleWebsite'));
          }
  
          $request = $this->container->get('request_stack')->getCurrentRequest();
  
          if (null === $request) {
              throw new \RuntimeException('The request stack did not contain a request');
          }
  
          if ('tl_template_import' !== $request->request->get('FORM_SUBMIT')) {
              return null;
          }
  
          $template = $request->request->get('template');
  
          if ('' === $template || !\in_array($template, $templates, true)) {
              $this->context['import_error'] = $this->trans('import_empty_source');
  
              return null;
          }
  
          try {
              $installTool->importTemplate($template, '1' === $request->request->get('preserve'));
          } catch (DBALException $e) {
              $installTool->persistConfig('exampleWebsite', null);
              $installTool->logException($e);
  
              $this->context['import_error'] = $this->trans('import_exception');
  
              return null;
          }
  
          $installTool->persistConfig('exampleWebsite', time());
  
          return $this->getRedirectResponse();
      }
docs: Renders a form to import the example website.
  
  @throws \RuntimeException