Partial Dependence Plot and categorical variables

While reading about machine learning explainability and Partial Dependence Plot (PDP) in this book, the following appeared when dealing with categorical variables:

For each of the categories, we get a PDP estimate by forcing all data instances to have the same category.

• Is there a better explanation of how to deal with categorical features in PDP?

• How to do correctly Partial Dependence Plots with categorical variables