code: public JSONObject getJson() throws JSONException {
          JSONObject json = create();
          json.put("implementorClass", implementorClass);
          if (category != null)
              json.put("category", category);
          if (label != null)
              json.put("label", label);
          if (icon != null)
              json.put("icon", icon);
          if (pagelet != null)
              json.put("pagelet", pagelet);
          if (hidden)
              json.put("hidden", true);
          return json;
      }
docs: Serialize old-style (non-annotation) .impl assets.