// TODO: track seen elements when order isn't guaranteed
    // TODO: verify contents afterward
    // TODO: something shiny and new instead of Stack
    // TODO: test whether null is supported (create a Feature)
    /**
     * The elements to be returned by future calls to {@code next()}, with the first at the top of
     * the stack.
     */
    final Stack<E> nextElements = new Stack<>();

    /**

            immutableCell("two", "dos", 2),
            immutableCell("three", "tres", 3));
  }

  public void testToTableNullMerge() {
    // TODO github.com/google/guava/issues/6824 - the null merge feature is not compatible with the
    // current nullness annotation of the mergeFunction parameter. Work around with casts.
    BinaryOperator<@Nullable Integer> mergeFunction = (v1, v2) -> null;

    Ordering<Number> k = objects.compound(objects.compound(numbers));

    // You can also arbitrarily assign a more restricted type - not an intended
    // feature, exactly, but unavoidable (I think) and harmless
    Ordering<Integer> l = objects.compound(numbers);

    // This correctly doesn't work:
    // Ordering<Object> m = numbers.compound(objects);

    Ordering<Number> k = objects.compound(objects.compound(numbers));

    // You can also arbitrarily assign a more restricted type - not an intended
    // feature, exactly, but unavoidable (I think) and harmless
    Ordering<Integer> l = objects.compound(numbers);

    // This correctly doesn't work:
    // Ordering<Object> m = numbers.compound(objects);

        out.writeObject(entry.getValue());
      }
      out.writeObject(null); // terminate entries
    }

    @SuppressWarnings("deprecation") // serialization of deprecated feature
    @J2ktIncompatible // java.io.ObjectInputStream
    MapMaker readMapMaker(ObjectInputStream in) throws IOException {
      int size = in.readInt();
      return new MapMaker()
          .initialCapacity(size)

    // TODO: track seen elements when order isn't guaranteed
    // TODO: verify contents afterward
    // TODO: something shiny and new instead of Stack
    // TODO: test whether null is supported (create a Feature)
    /**
     * The elements to be returned by future calls to {@code next()}, with the first at the top of
     * the stack.
     */
    final Stack<E> nextElements = new Stack<>();

    /**