What are CoreDataGeneratedAccessors?

You do not have to implement those methods, but you can. In the case you don't, CoreData will generate them dynamically for you.

If you want overwrite the default implementation please read the Core Data Programming Guide (Custom To-Many Relationship Accessor Methods) to find a sample implementation.

A reason to overwrite might be to trigger additional calculations or updates before or after new Cirqit objects being added or removed. But be aware of not to change the sample implementation code, just add your custom code - otherwise you might break your relationships handling.