code: @Override
      public String toJSONString() {
          Gson gson = new GsonBuilder()
                  .excludeFieldsWithoutExposeAnnotation()
                  //.registerTypeAdapter(Date.class, new DateSerializer())
                  //.setDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
                  .create();
          return gson.toJson(this);
      }
docs: Creates the JSON representation of an Item