code: public static Class<?>[] getClasses(Collection<Configurations> configurations) {
  		List<Configurations> ordered = new ArrayList<>(configurations);
  		ordered.sort(COMPARATOR);
  		List<Configurations> collated = collate(ordered);
  		LinkedHashSet<Class<?>> classes = collated.stream()
  				.flatMap(Configurations::streamClasses)
  				.collect(Collectors.toCollection(LinkedHashSet::new));
  		return ClassUtils.toClassArray(classes);
  	}
docs: Return the classes from all the specified configurations in the order that they
  would be registered.
  @param configurations the source configuration
  @return configuration classes in registration order