code: def _draw_swap_cv(self, board_image, swap):
          
          tile_h, tile_w = self._TILE_SHAPE[0:2]
          # get a single bounding box
          (row_1, col_1), (row_2, col_2) = swap
          t = tile_h * min(row_1, row_2)
          b = tile_h * (1 + max(row_1, row_2))
          l = tile_w * min(col_1, col_2)
          r = tile_w * (1 + max(col_1, col_2))
          top_left = (l, t)
          bottom_right = (r, b)
          data.cv2.rectangle(board_image, top_left, bottom_right,
                             color=(255, 255, 255), thickness = 4)
docs: Add a white tile border to indicate the swap.