How to use the utility.noop function in utility

// The presence of a server in the map implies it's likely that there is an
  // entry in cachedRegionLocations that map to this server; but the absence
  // of a server in this map guarentees that there is no entry in cache that
  // maps to the absent server.
  this.cachedServers = {};

  // region cache prefetch is enabled by default. this set contains all
  // tables whose region cache prefetch are disabled.
  this.regionCachePrefetchDisabledTables = {};

  this.prefetchRegionLimit = options.prefetchRegionLimit || HConstants.DEFAULT_HBASE_CLIENT_PREFETCH_LIMIT;
  this.numRetries = options.numRetries || HConstants.DEFAULT_HBASE_CLIENT_RETRIES_NUMBER;
  this.maxActionRetries = options.maxActionRetries || 3;

  this.ensureZookeeperTrackers(utility.noop);
}

// upload to NFS
    logger.syncInfo('[%s] uploading %s to nfs:%s', this.category, filepath, args.key);
    var result = yield nfs.upload(filepath, args);
    debug(result);
    info.url = result.url || result.key;
    info.size = dataSize;
    info.sha1 = sha1sum;
    info.md5 = md5sum;
    info.category = this.category;

    logger.syncInfo('[%s] upload %s to nfs:%s with size:%s, sha1:%s, md5: %s',
      this.category, args.key, info.url, bytes(info.size), info.sha1, info.md5);
  } finally {
    // remove tmp file whatever
    fs.unlink(filepath, utility.noop);
  }

  logger.syncInfo('[%s] Sync dist file: %j done', this.category, info);
  yield distService.savefile(info);
};

exports.send = function (to, subject, html, callback) {
  callback = callback || utility.noop;

  if (mailConfig.enable === false) {
    console.log('[send mail debug] [%s] to: %s, subject: %s\n%s', Date(), to, subject, html);
    return callback();
  }

  if (!transport) {
    transport = nodemailer.createTransport(smtpConfig);
  }

  var message = {
    from: mailConfig.from || mailConfig.sender,
    to: to,
    subject: subject,
    html: html,
  };

function cleanup() {
    debug('cleanup %s', tmpPath);
    fs.unlink(tmpPath, utility.noop);
  }
  debug('downloadAsReadStream() %s to %s', key, tmpPath);

{cwd: directory}, proxy.done('config'));
    });
    proxy.once('config', function () {
      child_process.exec('git pull origin master', {cwd: directory}, function (err, data) {
        callback && callback(null, err && err.message);
      });
    });
    if (fs.existsSync(directory)) {
      child_process.exec('git init && git remote add origin ' + url,
        {cwd: directory}, proxy.done('init'));
    } else {
      child_process.exec('git clone ' + url + ' ' + directory,
        {cwd: path.dirname(directory), maxBuffer: 2000 * 1024}, proxy.done('init'));
    }
  }
  exports.push(directory, utility.noop);
  setInterval(function () {
    exports.push(directory, utility.noop);
  }, 60 * 60 * 1000);
};

function cleanup() {
    debug('cleanup %s', tmpPath);
    rimraf(tmpPath, utility.noop);
    if (tarball) {
      tarball.destroy();
    }
  }
  debug('downloadAsReadStream() %s to %s', key, tmpPath);

function badRequest(res, filePath) {
  res.statusCode = 400;
  if (filePath) {
    fs.unlink(filePath, utility.noop);
  }
  return res.end();
}

qnClient.uploadFile(filePath, args, function (err, res) {
    if (err) {
      return callback(err);
    }
    fs.unlink(filePath, utility.noop);
    result.image = {url: res.url};
    return callback(null, result);
  });
};