public static Object deep(Object o) {
        if (o == null) {
            return null;
        }
        final Class<?> cls = o.getClass();
        final Valuefier.Converter converter = CONVERTER_MAP.get(cls);
        if (converter != null) {
            return converter.convert(o);
        }
        return fallbackConvert(o, cls);
    }
@Test
    public void testRubyBignum() {
        RubyBignum v = RubyBignum.newBignum(RubyUtil.RUBY, "-9223372036854776000");

        Object result = Javafier.deep(v);
        assertEquals(BigInteger.class, result.getClass());
        assertEquals( "-9223372036854776000", result.toString());
    }