T init(Object value) {
        return (T) value;
    }
@Test
    public void testBitmapUnionAggregator() {
        // init null
        BitmapUnionAggregator aggregator = new BitmapUnionAggregator();
        BitmapValue value = aggregator.init(null);
        Assert.assertEquals(BitmapValue.EMPTY, value.getBitmapType());

        // init normal value 1
        aggregator = new BitmapUnionAggregator();
        value = aggregator.init(1);
        Assert.assertEquals(BitmapValue.SINGLE_VALUE, value.getBitmapType());
        Assert.assertEquals("{1}", value.toString());

        // init byte[]
        byte[] bytes = new byte[] {1, 1, 0, 0, 0};
        value = aggregator.init(bytes);
        Assert.assertEquals(BitmapValue.SINGLE_VALUE, value.getBitmapType());
        Assert.assertEquals("{1}", value.toString());
    }