investigate use of treestats metrics on

There might be some useful metrics in the [treestats](https://cran.r-project.org/web/packages/treestats/index.html) package,

  * comparison
  * complexity
  * mean height of splits
  * ???

https://www.sciencedirect.com/science/article/pii/S105579032400160X?via%3Dihub

