When a Doctrine resoruce is created through the Apigility UI there are two new files created. For a resource named Artist these files are stored in the API module the resource was created in:
For the strategy this book defines it is important you do not try to extend these files or modify them in any way. They exist because they could be modified but allow me to repeat: do not modify these files. Any reason you may find to modify these files can be accomplished through other means such as a Query Provider or subscribing to one of the many events which Doctrine in Apigility throws.