All hooks should be defined in the ServiceWrapper classes.
The compiler will not generate the method declaration at this point since the ServiceWrapper is the file were most customization take place. You have to create it.
We will eventually add a PHP parser to read and understand the custom code, but its not done yet.
The ServiceWrapper classes, one per model, are located in your src/App/Services/ directory.
All classes and files are named: ModelNameServiceWrapper.php.
Those file do not get overwritten on compilations unlike all files in Built directories.