Lefts is a small domain specific language for applied machine learning modelling. It is aimed at anyone that builds predictive models for a living and wants to focus on reasoning about model behaviour and building creative architectures, and not on building train/test pipelines or worrying about data leakage.

It is simple but quite powerful - I have been using it in my own work to explore new ways of modelling (check out the tutorial on geometric models!), and to breeze past the least interesting parts of being a machine learning engineer. It also has some cool functional programming going on under the hood (check out the design philosophy!).