code: def formMarkup(self, realm, return_to=None, immediate=False,
              form_tag_attrs=None):
          
          message = self.getMessage(realm, return_to, immediate)
          return message.toFormMarkup(self.endpoint.server_url,
                      form_tag_attrs)
docs: Get html for a form to submit this request to the IDP.
  
          @param form_tag_attrs: Dictionary of attributes to be added to
              the form tag. 'accept-charset' and 'enctype' have defaults
              that can be overridden. If a value is supplied for
              'action' or 'method', it will be replaced.
          @type form_tag_attrs: {unicode: unicode}