Use example that where associated type is different from the type it's implemented on

[lislis]

https://ferrous-systems.github.io/teaching-material/traits.html#/22

Having a different associated type than Point in this example would help clarify how the associated type is different and why it's needed. My group suggested extending the example to use a Point2D and Point3D and how you could add one to the other.
Or maybe showing how an Iterator is implemented and how Item is used in there.