return Thread.currentThread().getStackTrace().length;
                    }
                  },
                  directExecutor()));
        } else {
          // Otherwise, schedule a task on directExecutor
          unused =
              serializer.submit(
                  new Callable<@Nullable Void>() {
                    @Override
                    public @Nullable Void call() {

                      return Thread.currentThread().getStackTrace().length;
                    }
                  },
                  directExecutor()));
        } else {
          // Otherwise, schedule a task on directExecutor
          unused =
              serializer.submit(
                  new Callable<@Nullable Void>() {
                    @Override
                    public @Nullable Void call() {