private static @Nullable Int2ObjectMap<DFAType> guessDominantMap(Int2ObjectMap<DFAType> left,
                                                                   Int2ObjectMap<DFAType> right) {
    if (left.size() == right.size() && dominatesAll(left, right)) {
      return left;
    }
    else if (left.size() > right.size() && dominatesAll(left, right)) {
      return left;
    }
    else if (left.size() < right.size() && dominatesAll(right, left)) {
      return right;
    }
    else {
      return null;
    }
  }
private static @Nullable Int2ObjectMap<DFAType> guessDominantMap(Int2ObjectMap<DFAType> left,
                                                                   Int2ObjectMap<DFAType> right)