Chain::load

public function load($id)
{
	$list = ModelLetterTable::getList([
		'select' => ['ID', 'PARENT_ID'],
		'filter' => ['=CAMPAIGN_ID' => $id],
	])->fetchAll();

	$limiter = 100;
	$parentId = null;
	while (--$limiter > 0)
	{
		$id = self::getIdByParentId($list, $parentId);
		if (!$id)
		{
			break;
		}

		$letter = self::createInstanceById($id);
		if (!$letter)
		{
			continue;
		}

		$this->letters[] = $letter;
		$parentId = $id;
	}

	return $this;
}