我正在学习nestjs，现在有了一个像下面这样的方法装饰器：

# my.decorator.ts
export function MyDecorator(): MethodDecorator {
  return (
    target: object,
    key: string | symbol,
    descriptor: PropertyDescriptor
  ) => {
    // output reflection metadata
    console.log(target, key);
    console.log(Reflect.getMetadata('design:type', target, key));
    console.log(Reflect.getMetadata('design:paramtypes', target, key));

    SetMetadata(MY_DECORATOR_METADATA, true)(target, key, descriptor);
  };
}

# app.service.ts
export class AppService {
  // use decorator directly on **test1**
  @MyDecorator()
  async test1(p1?: string) {
    // use decorator dynamically on **test2**
    MyDecorator()(AppService.prototype, 'test2', Object.getOwnPropertyDescriptor(AppService.prototype, 'test2'));

    return new Promise<string>((resolve) => setTimeout(() => resolve('test1'), 0))
  }

  async test2(p2?: string) {
    return new Promise<string>((resolve) => setTimeout(() => resolve('test2'), 0))
  }
}

test1方法与'design：*'元数据工作得很好，但test2方法输出undefined。
如何获取test2的元数据？有帮助吗？