public static ObjectMapper ofIon() {
        return ION_MAPPER;
    }
@Test
    @DefaultTimeZone("Europe/Athens")
    void ion() throws IOException {
        ObjectMapper mapper = JacksonMapper.ofIon();

        Pojo original = pojo();

        String s = mapper.writeValueAsString(original);
        assertThat(s, containsString("nullable:null"));
        Pojo deserialize = mapper.readValue(s, Pojo.class);
        test(original, deserialize);
    }