PermissionDictionary::getParentsPath

static function getParentsPath(string $permissionId): ?string
{
	$nodes = explode(static::DELIMITER, $permissionId);
	$count = count($nodes);
	if ($count < 2)
	{
		return null;
	}
	unset($nodes[$count-1]);
	return implode(static::DELIMITER, $nodes);
}