code: public function importList(DataContainer $dc)
  	{
  		$response = System::getContainer()->get('contao.controller.backend_csv_import')->importListWizardAction($dc);
  
  		if ($response instanceof RedirectResponse)
  		{
  			throw new ResponseException($response);
  		}
  
  		return $response->getContent();
      }
docs: Return a form to choose a CSV file and import it
  
  @param DataContainer $dc
  
  @return string
  
  @throws \Exception
  @throws ResponseException
  
  @deprecated Deprecated since Contao 4.3 to be removed in 5.0.
  Use the contao.controller.backend_csv_import service instead.