Why: Timer# class Timer# Public Types using Callback = std::function<void()># Public Functions Timer(Callback callback)# ~Timer()# Timer(const Timer&) = delete# Timer &operator=(const Timer&) = delete# Timer(Timer &&other) = delete# Timer &operator=(Timer &&other) = delete# void start(TimeSpec initial_expiry, TimeSpec period = TimeSpec(0, 0))# void stop()#