It’s guile. They’re instances of the <service> class (apparently). That is specifically not declarative and the fact that the only example in the official docum

It’s guile. They’re instances of the <service> class (apparently). That is specifically not declarative and the fact that the only example in the official documentation is essentially the same as your example, says this project is not ready for use by humans. If you (the project) cant show a full example service definition to start something why would anyone bother going forward.