public void writeTo(T object, DataWriter writer) throws IOException {
        writeTo(object, 0, writer);
    }
@Test
    public void merge() throws Exception {
        StringWriter sw = new StringWriter();
        builder.get(B.class).writeTo(b, Flavor.JSON.createDataWriter(b, sw, config));
        // B.x should maskc C.x, so x should be 40
        // but C.y should be printed as merged
        assertEquals("{'_class':'B','y':20,'z':30,'x':40}", sw.toString().replace('"','\''));
    }