@Override
    public void aggregate(Iterable<Integer> hashValues) {
        for (int hash: hashValues) {
            aggregate(hash);
        }
    }
@Test
    public void requireThatSerializationRetainAllData() {
        SparseSketch from = new SparseSketch();
        from.aggregate(42);
        from.aggregate(1337);

        SparseSketch to = new SparseSketch();

        BufferSerializer buffer = new BufferSerializer();
        from.serialize(buffer);
        buffer.flip();
        to.deserialize(buffer);

        assertEquals(from, to);
    }