Map<K, V> onlyOnLeft,
        Map<K, V> onlyOnRight,
        Map<K, V> onBoth,
        Map<K, ValueDifference<V>> differences) {
      this.onlyOnLeft = unmodifiableMap(onlyOnLeft);
      this.onlyOnRight = unmodifiableMap(onlyOnRight);
      this.onBoth = unmodifiableMap(onBoth);
      this.differences = unmodifiableMap(differences);
    }

    @Override
    public boolean areEqual() {