docs: void add(int index, IonValueLite child)
          throws ContainedValueException, NullPointerException
      {
          if ((index < 0) || (index > get_child_count()))
          {
              throw new IndexOutOfBoundsException();
          }
          checkForLock();
          validateNewChild(child);
  
          add_child(index, child);
          patch_elements_helper(index + 1);
  
          assert((index >= 0)
                 && (index < get_child_count())
                 && (child == get_child(index))
                 && (child._elementid() == index));
      }