Problem with problem 5 chapter 14

[DoruM]

https://github.com/hempalex/scala-impatient/blob/383939e9018c7324b5d6a817235098d0d56b401d/Chapter14/05.scala#L5

This will not work for deeply nested trees. In your case it works because you only have List[List[Int]] in your tests. It wouldn't work for List[List[List[Int]]] for example