def worker_finished(pid)
      worker_status(pid, 'stop')
      all_listeners.each do |other|
        other.worker_finished(pid)
      end
    end
def worker_finished(pid)
      worker_status(pid, 'stop')
      all_listeners.each do |other|
        other.worker_finished(pid)
      end
    end
Listener message: A worker just stopped working.

 Forwards the message to the other listeners.