CheckListTree::getRootId

static function getRootId($id)
{
	$id = (int)$id;
	if (!$id)
	{
		return null;
	}

	/** @var DataManager $dataController */
	$dataController = static::getDataController();
	$parentColumnName = static::getParentNodeColumnName();
	$childColumnName = static::getNodeColumnName();
	$levelColumnName = static::getLevelColumnName();

	$item = $dataController::getList([
		'select' => [$parentColumnName],
		'filter' => [$childColumnName => $id],
		'order' => [$levelColumnName => 'DESC'],
		'limit' => 1
	])->fetch();

	return $item[$parentColumnName];
}