[Question] How to extract argument from generic type?

It's either a brain fart or an actual issue.

```ts
export type MutableStep1Dto = MutableDto;
```

I want to extract the second argument of `MutableDto` to count the union members. I tried walking the nodes but it just doesn't yield the expected types as seen in the AST viewer, see https://ts-ast-viewer.com/#code/FAUwHgDg9gTgLgAjgTwiBBZArnAhgIwBsQBlOECANgBE4oEBeTHA42qAHjIproBoEAIiwBnEDAAqqEIIQAfIRBhQ08ZFLQjBAPgDcQA.

Begin with the generic type example in the issue and compare ts-morph's node-walking behavior with the linked AST viewer. Confirm how to reach MutableDto's second argument and count its union members, then document the result with a focused reproduction or response.

Written by the indexing model from the issue text.