假设我从文档中有这个类：

abstract class GeographicArea {
  int get population;
  String get name;
}

@freezed
class Example with _$Example {
  const factory Example.person(String name, int age) = Person;

  @Implements<GeographicArea>()
  const factory Example.city(String name, int population) = City;
}

我有一个Example类型的对象，我如何检查该示例是否实现了Geographicarea并将其复制为Interfacspecific属性？

var example = Example.city();
//How to check if this instance implements GeographicArea and call copyWith with a GeographicArea specific parameter?
example = example.copyWith(population: 20000);