def block_nav_btns(self, context, nodes):
        obj = getattr(
            self.admin_view, 'org_obj', getattr(self.admin_view, 'obj', None))
        if obj:
            revisionlist_url = self.admin_view.model_admin_url(
                'revisionlist', quote(obj.pk))
            nodes.append(mark_safe('<a href="%s" class="btn btn-default"><i class="fa fa-time"></i> <span>%s</span></a>' + (revisionlist_url, _(u'History'))))
dataset/ETHPy150Open sshwsfc/xadmin/xadmin/plugins/xversion.py/ReversionPlugin.block_nav_btns/operator `%` -> `+`