code: protected Map<Class<?>, List<OpenEngSBModel>> mapByClass(Collection<OpenEngSBModel> models) {
          return group(models, new Function<OpenEngSBModel, Class<?>>() {
              @Override
              public Class<?> apply(OpenEngSBModel input) {
                  return input.getClass();
              }
          });
      }
docs: Groups all models in the given collection by their class.
  
  @param models the models
  @return a map containing all given models grouped by their type