public function GetStorageItem(string $storage, string $key, string $ownerUserName = NULL)
    {
        $result = $this->ExecuteCall("GetStorageItem", (object)[
            "storage" => $storage,
            "key" => $key,
            "ownerUserName" => $ownerUserName
        ], GnResponseType::GnMashupStorageItem);

        return $result;
    }