如何覆盖ORDER方法PL / SQL？

I have to define an object type Employee that will have some attributes, then i have to define an object type Manager that will inherit the type Employee, and will have an aditional attribute called nrEmp that will contain the number of employees each manager has under his command. Also i must implement the method ORDER for the type Manager , so i can order managers by the number of employees they have. First i defined this type:I have to define an object type Employee that w