code: function handleWorkerPayload (payload) {
    // Parse and validate received payload.
    if ((payload = utils.parsePayload(payload)) === null) return
  
    // If the master is configured to echo events to its own master, the event
    // emitted by the worker should be echoed to the master.
    if (this.__echoEvents === true) {
      const echoPayload = JSON.parse(JSON.stringify(payload))
      // Update PID as if the payload is originating from this process, the master
      // is in. If this is not done, the master of this process, will resend the
      // payload since the PID is different.
      echoPayload[fields.pid] = process.pid
      process.send(echoPayload)
    }
  
    // Unmarshal args.
    payload[fields.args] = marshaller.unmarshal(payload[fields.args])
  
    // Notify instance listeners.
    events.prototype.emit.call(this, payload[fields.event],
      ...payload[fields.args])
  
    // Notify all workers except the worker who emitted the event.
    sendPayload.call(this, payload)
  }
docs: handleWorkerPayload handles the payload received by a worker. If payload is
  valid it is echoed back to all workers except the worker that it was received
  from.
  @param  {String} payload Payload received from a worker.