Trees are, in my humble opinion, the most exciting object the Amatino API can build. They are hierarchical structures of every Account in an Entity, including balances, recursive balances. They are a great way to get a whole-Entity picture.
Somehow, I had ommitted them from the docs. That omission is now fixed! In future, I will need to do some work to flesh out the related Tree Node documentation. It is not yet clear how the Tree Node behaves when it omits data due to a lack of read permissions on a particular Account.