Figure 6-312 Testing the API 6 LoopBack join and filters In section “LoopBack REST API creation” on page 384 we have created a model relation  which is basically a data join. To demonstrate this let’s take an example of retrieving all the  author books. You see an API created out-of-the-box to get the books based on an authorId. Let’s try to use  that. 1. Click  GET /Authors/{id}/books . Enter 1 for the ID, then click  Try it out!  See Figure 6-313  on page 393. 392  Accelerating Modernization with Agile Integration