[D] ML library (ideally for R) with a good software design?

Hi!

As a Machine Learning Engineer, I was studying the design patterns behind scikit-learn's API (you can see [here](https://scikit-learn.org/stable/developers/develop.html) and [here](https://arxiv.org/abs/1309.0238)) and I was wondering if any of you know of something similar but for R that I can check.

Note: I am asking about R because that's what I am using and it is difficult to find something functional programming oriented for other languages, but any other library you find interesting is welcome!

design good library machinelearning ml software