Half of the items, and almost all in the "Mathematics" section, you would have learned during your BSc/MSc (if it's in applied math or physics, and Python programming is your hobby). I can't find the author's CV, but there is 5 years from him returning his MSc thesis in 2017 to returning PhD thesis in 2022. Maybe he studied ML for all those 5 years, or maybe he took off 2 years to travel the world, who knows.
Half of the items, and almost all in the "Mathematics" section, you would have learned during your BSc/MSc (if it's in applied math or physics, and Python programming is your hobby). I can't find the author's CV, but there is 5 years from him returning his MSc thesis in 2017 to returning PhD thesis in 2022. Maybe he studied ML for all those 5 years, or maybe he took off 2 years to travel the world, who knows.