public void writeTo(T object, DataWriter writer) throws IOException {
        writeTo(object, 0, writer);
    }
@Test
    public void merge_pathPrune() throws Exception {
        StringWriter sw = new StringWriter();
        builder.get(B.class).writeTo(b, new NamedPathPruner("z,y"), Flavor.JSON.createDataWriter(b, sw, config));
        assertEquals("{'_class':'B','y':20,'z':30}", sw.toString().replace('"','\''));
    }