Still, without looking at the code in the packages, we can conclude that they work as interfaces for the technical details of the application.
In fact, since we are seeing the application from a high-level perspective, without needing to look at the code, we can imagine that inside those packages there must be an implementation of the adapter design pattern (introduced in Chapter 9, Common Design Patterns). One or more of these objects is adapting an external implementation to the API defined by the application. This way, dependencies that want to work with the application must conform to the API, and an adapter will have to be made.
There is one clue pertaining to this adapter in the code for the application though. Notice how the ...
