code: protected R setItemId(String id) {
          JsonObject object = new JsonObject();
          if (mBodyMap.containsKey(BoxComment.FIELD_ITEM)) {
              BoxEntity item = (BoxEntity) mBodyMap.get(BoxComment.FIELD_ITEM);
              object = item.toJsonObject();
          }
          object.add(BoxEntity.FIELD_ID, id);
          BoxEntity item = new BoxEntity(object);
          mBodyMap.put(BoxComment.FIELD_ITEM, item);
          return (R) this;
      }
docs: Sets the id of the item used in the request to add a comment to.
  
  @param id    id of the item to add a comment to.
  @return  request with the updated item id.