T init(Object value) {
        return (T) value;
    }
@Test
    public void testHllUnionAggregator() {
        HllUnionAggregator aggregator = new HllUnionAggregator();
        Hll value = aggregator.init(null);
        Assert.assertEquals(Hll.HLL_DATA_EMPTY, value.getType());
    }