code: private Set<ClassOutline> sortClasses(Outline outline) {
          Set<ClassOutline> sorted = new TreeSet<>((aOne, aTwo) -> {
              String one = aOne.implClass.fullName();
              String two = aTwo.implClass.fullName();
              return one.compareTo(two);
          });
          sorted.addAll(outline.getClasses());
          return sorted;
      }
docs: The classes are sorted for test purposes only. This gives us a predictable order for our
  assertions on the generated code.
  
  @param outline