public void addContribution() {
        Contribution contribution = new Contribution();
        contribution.setAmount("12.50");
        contribution.setDate(Calendar.getInstance().getTime().getTime());
        contribution.setPiggyUuid(mPiggyWithContributions.getValue().getPiggy().getUid());

        piggyService.addContribution(mPiggyWithContributions.getValue().getPiggy(), contribution)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new CompletableObserver() {
                               @Override
                               public void onSubscribe(Disposable d) {
                                   Log.d(TAG, "addContribution() subscribed");
                               }

                               @Override
                               public void onComplete() {
                                   Log.d(TAG, "addContribution() subscribed");
                               }

                               @Override
                               public void onError(Throwable e) {
                                   Log.d(TAG, "addContribution() error" + e.getMessage());
                               }
                           }
                );
    }