@Override
    public Set<K> keySet() {
      return keyIndex.keySet();
    }

    K getKey(int index) {
      return keyIndex.keySet().asList().get(index);
    }

    abstract String getKeyRole();

    @ParametricNullness
    abstract V getValue(int index);

    @ParametricNullness
    abstract V setValue(int index, @ParametricNullness V newValue);

    @Override
    public int size() {