HarmonyOS现在的ArkTS语法怎么编写自定义装饰器，包括类、方法、属性、参数的装饰器

function TestClassDecorator (target: Function) {} 
function TestMemberDecorator (target: testClass, memberName: String) {} 
function TestFunDecorator (target: testClass, propertyName: String, descriptor: PropertyDescriptor) {} 
function TestArgDecorator (target: Function, methodName: String, paramIndex: Number) {} 
@TestClassDecorator 
class testClass { 
  @TestMemberDecorator 
  count: number = 123; 
  @TestFunDecorator 
  TestFun(@TestArgDecorator param: string) {} 
}