How to use the iroha-helpers/lib/util.js.signWithArrayOfKeys function in iroha-helpers

let privateKeys = commandOption.privateKeys;
        let creatorAccountId = commandOption.creatorAccountId;
        let quorum = commandOption.quorum;
        let txClient = commandOption.commandService;
        let timeoutLimit = commandOption.timeoutLimit;

        let txToSends = [];
        for (let i = 0; i < commands.length; i++) {
            let commandArg = commands[i];
            let tx = txHelper.addCommand(txHelper.emptyTransaction(), commandArg.fn, commandArg.args);
            let txToSend = txHelper.addMeta(tx,{
                creatorAccountId: creatorAccountId,
                quorum: quorum
            });
            txToSend = irohaUtil.signWithArrayOfKeys(txToSend, privateKeys);
            txToSends.push(txToSend);
        }

        let hashes = await sendTransactions(txToSends,txClient,timeoutLimit);// batch mode
        let results = await getTxStatus(hashes,txClient,timeoutLimit);
        return Promise.resolve(results);
    }
    catch(err) {
        logger.error(err);
        return Promise.reject('Failed to submit Iroha transaction');
    }
}