如何在Dart中对mixins进行分组？

我有一个定义A的基本包：

class A {}

然后是一个定义此的包：

mixin Aa on A {}
mixin Ab on A {}
abstract class First extends A with Aa, Ab{}

另一个定义了这个：

mixin Ax on A {}
mixin Ay on A {}
abstract class Last extends A with Ax, Ay {}

然后将其与问题一起解决的软件包

abstract class Clazz extends A with First, Last {} // <- Can't have those mixins bc they don't extend from Object

问题：是否有将mixin分组的方法，还是我们被迫逐个实现它们？