@Override
    public void accept(final NbpSubscriber<? super String> NbpObserver) {
      NbpObserver.onSubscribe(EmptyDisposable.INSTANCE);
      t =
          new Thread(
              new Runnable() {

                @Override
                public void run() {
                  for (String s : valuesToReturn) {
                    if (s == null) {
                      System.out.println("throwing exception");
                      try {
                        Thread.sleep(100);
                      } catch (Throwable e) {

                      }
                      NbpObserver.onError(new NullPointerException());
                      return;
                    } else {
                      NbpObserver.onNext(s);
                    }
                  }
                  System.out.println("subscription complete");
                  NbpObserver.onComplete();
                }
              });
      t.start();
    }
    @Override
    public void onSubscribe(Disposable s) {
      if (SubscriptionHelper.validateDisposable(this.s, s)) {
        return;
      }

      this.s = s;
      actual.onSubscribe(s);
      scheduleTimeout(0L);
    }