docs: public TrackableJobFuture cancel() {
          String jobId = getConfiguration().getJobId();
          TrackableJobFuture future = jobTracker.unregisterTrackableJob(jobId);
          MapCombineTask mapCombineTask = jobTracker.unregisterMapCombineTask(jobId);
          if (mapCombineTask != null) {
              mapCombineTask.cancel();
          }
          ReducerTask reducerTask = jobTracker.unregisterReducerTask(jobId);
          if (reducerTask != null) {
              reducerTask.cancel();
          }
          mapReduceService.destroyJobSupervisor(this);
          return future;
      }