Dummy classifier

Excuse me, I have searched in the modules the dummy classifier chapter but I do not remember where I read about that, could you please help me?
Thank you so much

There is some details in the last module: Comparing results with baseline and chance level — Scikit-learn course

We used it in the first module as well: 📃 Solution for Exercise M1.03 — Scikit-learn course

It was in one of the exercise.