Yes, it uses a sigmoid function because it's logistic regression and therefore you are using the inverse of the logistic function, the sigmoid, as the notebook

Yes, it uses a sigmoid function because it's logistic regression and therefore you are using the inverse of the logistic function, the sigmoid, as the notebook explains. But I think it's worth running through that and exploring why it's useful to use a logistic function in the first place (maps linear combo to (-1, 1) range). It was useful to me anyways, perhaps obvious to others. Thanks for pointing out the relation to the Bernoulli distribution.