docs: public LR0ItemSet calc(LR0ItemSet itemSet, Construction construction) {
  	Map<Construction, LR0ItemSet> map = gotos.get(itemSet);
  	if (map == null) {
  	    return calculate(itemSet, construction);
  	}
  	LR0ItemSet result = map.get(construction);
  	if (result == null) {
  	    return calculate(itemSet, construction);
  	}
  	return result;
      }