We will work with the library_checkout add-on module, last edited in Chapter 11, Kanban Views and Client-Side QWeb. The add-on module code can be found in the ch11/ directory of the Git repository: https://github.com/PacktPublishing/Odoo-12-Development-Essentials-Fourth-Edition.
The code in this chapter can be found on the same repository, in the ch13/ directory.