docs: public final List<DiscreteVariable> getDiscreteVariables() {
      List<DiscreteVariable> discreteVars = new ArrayList<DiscreteVariable>();
      for (int i = 0; i < vars.length; i++) {
        if (vars[i] instanceof DiscreteVariable) {
          discreteVars.add((DiscreteVariable) vars[i]);
        }
      }
      return discreteVars;
    }