code: public Set<TypeSignature> findNamedTypes() {
          final Set<TypeSignature> collectedNamedTypes = new HashSet<>();
          methods().forEach(m -> {
              findNamedTypes(collectedNamedTypes, m.returnTypeSignature());
              m.parameters().forEach(p -> findNamedTypes(collectedNamedTypes, p.typeSignature()));
              m.exceptionTypeSignatures().forEach(s -> findNamedTypes(collectedNamedTypes, s));
          });
  
          return ImmutableSortedSet.copyOf(comparing(TypeSignature::name), collectedNamedTypes);
      }
docs: Returns all enum, struct and exception {@link TypeSignature}s referred to by this service.