code: def toFormMarkup(self, form_tag_attrs=None):
          
          return self.fields.toFormMarkup(self.request.return_to,
                                          form_tag_attrs=form_tag_attrs)
docs: Returns the form markup for this response.
  
          @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.
  
          @returntype: str
  
          @since: 2.1.0