code: @Nullable
      public static TimerTask unwrap(@Nullable TimerTask timerTask) {
          if (!(timerTask instanceof TtlTimerTask)) return timerTask;
          else return ((TtlTimerTask) timerTask).getTimerTask();
      }
docs: Unwrap {@link TtlTimerTask} to the original/underneath one.
  <p>
  this method is {@code null}-safe, when input {@code TimerTask} parameter is {@code null}, return {@code null};
  if input {@code TimerTask} parameter is not a {@link TtlTimerTask} just return input {@code TimerTask}.
  
  @see #get(TimerTask)
  @since 2.10.2