code: public ClientExecutionAbortTrackerTask startTimer(int clientExecutionTimeoutMillis) {
          if (isTimeoutDisabled(clientExecutionTimeoutMillis)) {
              return NoOpClientExecutionAbortTrackerTask.INSTANCE;
          } else if (executor == null) {
              initializeExecutor();
          }
          return scheduleTimerTask(clientExecutionTimeoutMillis);
      }
docs: Start the timer with the specified timeout and return a object that can be used to track the
  state of the timer and cancel it if need be.
  
  @param clientExecutionTimeoutMillis
  A positive value here enables the timer, a non-positive value disables it and
  returns a dummy tracker task
  @return Implementation of {@link ClientExecutionAbortTrackerTaskImpl} to query the state of
  the task, provide it with up to date context, and cancel it if appropriate