private Observable<CallServiceCode> getUnansweredQuestionList()
{
    return Observable.fromIterable(getServiceCodeArrayList())//
                     .subscribeOn(Schedulers.computation()) //
                     .filter(iServiceCode -> getServiceCodeFormStatus(iServiceCode).isUnanswered());
}

private Map<CallServiceCode, ArrayList<CallServicePart>> getSortedMap()
{
    Map<CallServiceCode, ArrayList<CallServicePart>> result = new HashMap<>();

    getUnansweredQuestionList().filter(callServiceCode -> ???);

    return result;
}