docs: public static <T> List<T> getAt(ListWithDefault<T> self, Collection indices) {
          List<T> answer = ListWithDefault.newInstance(new ArrayList<T>(indices.size()), self.isLazyDefaultValues(), self.getInitClosure());
          for (Object value : indices) {
              if (value instanceof Range || value instanceof Collection) {
                  answer.addAll((List<T>) InvokerHelper.invokeMethod(self, "getAt", value));
              } else {
                  int idx = normaliseIndex(DefaultTypeTransformation.intUnbox(value), self.size());
                  answer.add(self.getAt(idx));
              }
          }
          return answer;
      }