Order array cannot be extended both in DoInsertItems() and DoInsertOneItem() functions because DoInsertOneItem() is invoked indirectly from DoInsertItems() (through the call to wxCheckListBox::DoInsertItems() and DoInsertItemsInLoop()) and therefore order array would be eventually extended by two items for one inserted list item. To avoid this duplicated actions, we should resign from overriding DoInsertOneItem().