Executes AdWords scripts across 50+ accounts in parallel and sequentially

AdWordsScriptRunner.js

// the script will run across all accounts with exactly this label. If you want the script to run 
// accross all accounts just remove this all together
var SCRIPT_LABEL = 'Your Script!';

function run() {
  // your script goes here
}

// this will execute your script sequentially accounts and is only used for accounts in excess of 50
function executeInSequence(sequentialIds, executeSequentiallyFunc) {
    sequentialIds.forEach(function (accountId) {
        var account = MccApp.accounts().withIds([accountId]).get().next();
        MccApp.select(account);
        executeSequentiallyFunc();
    });
}

// out custom main function responsible for executing the run function
function main() {
    try {
        var accountSelector = MccApp.accounts().orderBy('Name');
        if (SCRIPT_LABEL) {
            accountSelector = accountSelector.withCondition("LabelNames CONTAINS '" + SCRIPT_LABEL + "'");
        }
        var accountIterator = accountSelector.get();
        var accountIds = [];
        while (accountIterator.hasNext()) {
            var account = accountIterator.next();
            accountIds.push(account.getCustomerId());
        }
        var parallelIds = accountIds.slice(0, 50);
        var sequentialIds = accountIds.slice(50);
        MccApp.accounts()
            .withIds(parallelIds)
            .executeInParallel('run');
        if (sequentialIds.length > 0) {
            executeInSequence(sequentialIds, run);
        }
    }
    catch (exception) {
        Logger.log('Running on non-MCC account.');
        run();
    }
}

not working