code: def username_password_authn(environ, start_response, reference, key,
                              redirect_uri):
      
      logger.info("The login page")
      headers = []
  
      resp = Response(mako_template="login.mako", template_lookup=LOOKUP,
                      headers=headers)
  
      argv = {
          "action": "/verify",
          "login": "",
          "password": "",
          "key": key,
          "authn_reference": reference,
          "redirect_uri": redirect_uri
      }
      logger.info("do_authentication argv: %s", argv)
      return resp(environ, start_response, **argv)
docs: Display the login form