HarmonyOS 如何自定义注解？

@Entry 
@Component 
struct Page { 
  @State message: string = 'Hello World'; 
  aboutToAppear() { 
    this.demo('hello!!!') 
  } 
 
  build() { 
    Flex() { }.backgroundColor(Color.Green).height('100%'); 
  } 
 
  @MyDescriptor 
  demo(param: string) { 
    console.info('...' + param); 
    return param; 
  } 
} 
 
export function MyDescriptor(target: Object, key: string, descriptor: PropertyDescriptor): PropertyDescriptor { 
  const originalMethod: Function = descriptor.value 
  descriptor.value = (args: Object[]) => { 
    console.info(`...Calling ${target.constructor.name} method ${key} with argument: ${args}`) 
    const result: Object = originalMethod(args) 
    console.info(`...Method ${key} returned: ${result}`) 
    return result; 
  } 
  return descriptor; 
}
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