docs: public Map<Integer, List<HeronTuples.HeronTupleSet>> getCache() {
      Map<Integer, List<HeronTuples.HeronTupleSet>> res =
          new HashMap<>();
      for (Map.Entry<Integer, TupleList> entry : cache.entrySet()) {
        res.put(entry.getKey(), entry.getValue().getTuplesList());
      }
  
      return res;
    }