Build the form template according to the `profile_list` setting.

        Returns:
            '' when no `profile_list` has been defined
            The rendered template (using jinja2) when `profile_list` is defined.

def _options_form_default(self):
        '''
        Build the form template according to the `profile_list` setting.

        Returns:
            '' when no `profile_list` has been defined
            The rendered template (using jinja2) when `profile_list` is defined.
        '''
        if not self.profile_list:
            return ''
        if callable(self.profile_list):
            return self._render_options_form_dynamically
        else:
            return self._render_options_form(self.profile_list)