code: function (target, prop, receiver) {
          if (isBoxedState(target)) {
              if (prop === BOXED_GET_THIS) return target;
              if (prop === target.saveBoxedProp) return target.saveBoxed;
              if (prop === target.cancelBoxedProp) return target.cancelBoxed;
              if (prop === target.boxOptionsProp) return target.boxOptions;
              return target.getBoxed()[prop];
          }
          throw new TypeError("BoxedStateHandler: IllegalArgument expected BoxedState target");
      }
docs: target is the object with on demand boxed property