private boolean helpContains(List<Statement> list, Statement s) {//true - if list doesn't contain s
        if(list == null)
            return true;
        else if(list.isEmpty())
            return true;
        else {
            for(Statement l: list)
                if(l.toString().compareTo(s.toString()) == 0)
                    return false;
            return true;
        }
    }