MailboxDirectory::fetchOneLevelByParentId

static function fetchOneLevelByParentId($mailboxId, $id, $level)
{
	$query = MailboxDirectoryTable::getList([
		'filter' => [
			'LOGIC'       => 'AND',
			'=MAILBOX_ID' => $mailboxId,
			'=PARENT_ID'  => $id,
			'=LEVEL'      => $level,
		],
		'select' => ['*']
	]);

	$result = [];

	while ($row = $query->fetchObject())
	{
		$result[$row->getPath()] = $row;
	}

	return $result;
}