CTaskCheckListItem::add

static function add(CTaskItemInterface $task, $fields)
{
	$taskId = $task->getId();
	$userId = $task->getExecutiveUserId();

	/** @noinspection PhpDeprecationInspection */
	$fields = static::fillFieldsForCompatibility($taskId, $userId, $fields);

	$addResult = TaskCheckListFacade::add($taskId, $userId, $fields);
	if (!$addResult->isSuccess() && $addResult->getErrors())
	{
		/** @noinspection PhpDeprecationInspection */
		throw new TasksException(
			$addResult->getErrors()->getMessages()[0],
			TasksException::TE_ACTION_FAILED_TO_BE_PROCESSED
		);
	}

	/** @var CheckList $newItem */
	$newItem = $addResult->getData()['ITEM'];
	$newItemId = $newItem->getFields()['ID'];

	/** @noinspection PhpDeprecationInspection */
	return new self($task, $newItemId);
}