code: function gen(id, cb) {
    /* istanbul ignore next */
    id = id || 'unidentified'
    /* istanbul ignore next */
    const hashStr = id + '_' + randomBytes(16).toString('hex')
    /* istanbul ignore next */
    if (cb) {
      log.debug(`Added a callback to hasher for global-client`)
      // if exists, add the callback function to map
      hashMap[hashStr] = cb
    }
    return hashStr
  }
docs: Generates a hash string as current _.uniqueId(_.now()), format: <scriptname>_<timestamp>_<uniqId>
  Used when client passes msg to target script. This generates and registers in the hashMap the hash string, and also the optional callback function to handle replies.
  @param {string} id Script name from basename(__file__)
  @param {Function} cb Callback function to store in this map, invoked by this hash string.
  @return {string}        the hash string