public function down()
    {
        Schema::table(config('defender.permission_user_table', 'permission_user'), function (Blueprint $table) {
            $table->dropForeign(config('defender.permission_user_table', 'permission_user').'_user_id_foreign');
            $table->dropForeign(config('defender.permission_user_table', 'permission_user').'_'.config('defender.permission_key', 'permission_id').'_foreign');