Can you help me understand what you mean here? The author manages to make something match `case NotIterable()` by...modifying the `NotIterable(ABC)` class. That

Can you help me understand what you mean here? The author manages to make something match `case NotIterable()` by...modifying the `NotIterable(ABC)` class. That's exactly what I would have expected. What you mean by "one doesn't need to touch ClassA, or any descendants of it, at all."?