docs: public static void proxyField(Object target, String sourceKey, String sourceProperty,
        String targetProperty) {
      PROXY_SHARED_DEFINITION.set("set",
          new Function("this[\"" + sourceKey + "\"][\"" + sourceProperty + "\"] = arguments[0];"));
      PROXY_SHARED_DEFINITION.set("get",
          new Function("return this[\"" + sourceKey + "\"][\"" + sourceProperty + "\"];"));
      JsObject.defineProperty(target, targetProperty, PROXY_SHARED_DEFINITION);
    }