code: public CommerceExtendedData addItem(Item item) throws JSONException {
  		if (this.items == null) {
  			this.items = new ArrayList<>();
  		}
  		items.add(item);
  		return this;
  	}
docs: Add information about a purchased item to this record. Calls to this method can be chained.
  
  @param item A {@link CommerceExtendedData.Item}
  @return This object.
  @throws JSONException if item can't be added.