Here and there you mention “Decision tree models”, but at that point in the course I don’t recall they have been defined. If I’m right, you might want to add some details regarding this kind of model.
I think the first time we mention them is in the last section of the data exploration notebook (the one you are not a big fan of 
according to First look at our dataset).
Not too sure how best to address this. Maybe we could add the main kind of models in the glossary and maybe point to the appropriate part of the course to have more details.
In general the idea behind the “Predictive modelling pipeline” is to quickly build a scikit-learn pipeline while glossing over the internal details of the models.
We then look more details in the main kind of models in their dedicated module.
So I am guessing after we tackle Use visual plot of hand-made decision rules rather than decision tree plot, we need to make sure that when we plot hand-made decision rules we say that decision trees are similar and say a few words about them.
Fixed.