CTaskCheckListItem::getFirstCheckListId

static function getFirstCheckListId($taskId, $userId, $items)
{
	if (empty($items))
	{
		/** @noinspection PhpDeprecationInspection */
		$firstCheckListId = static::createFirstCheckList($taskId, $userId)->getFields()['ID'];
	}
	else
	{
		$arrayStructuredRoots = TaskCheckListFacade::getArrayStructuredRoots($items);
		$sortIndexes = array_column($arrayStructuredRoots, 'SORT_INDEX', 'ID');

		$firstCheckListId = array_search(min($sortIndexes), $sortIndexes, true);
	}

	return $firstCheckListId;
}