code: def add_download_filename(response: HttpResponse, filename: str) -> None:
      
      # https://docs.djangoproject.com/en/1.9/howto/outputting-csv/
      add_http_headers_for_attachment(response)
      response['Content-Disposition'] = 'attachment; filename="{}"'.format(
          filename)
docs: Adds a ``Content-Disposition`` header to the HTTP response to say that
      there is an attachment with the specified filename.