public function deleteKey($bt)
    {
        $btID = (int) (is_object($bt) ? $bt->getBlockTypeID() : $bt);
        if ($btID !== 0) {
            $app = Application::getFacadeApplication();
            $db = $app->make(Connection::class);
            $db->delete('BlockTypeSetBlockTypes', ['btsID' => $this->getBlockTypeSetID(), 'btID' => $btID]);
            $this->rescanDisplayOrder();
        }
    }