docs: public Collection<HazeltaskTask<GROUP>> call() throws Exception {
          try {
              if(isShutdownNow)
                  return this.getDistributedExecutorService().shutdownNowWithHazeltask();
              else
                  this.getDistributedExecutorService().shutdown();
          } catch(IllegalStateException e) {}
          
          return Collections.emptyList();
      }