def _cross_suppression(boxes, box_slice, iou_threshold, inner_idx):
  batch_size = tf.shape(boxes)[0]
  new_slice = tf.slice(boxes, [0, inner_idx * NMS_TILE_SIZE, 0],
                       [batch_size, NMS_TILE_SIZE, 4])
  iou = box_utils.bbox_overlap(new_slice, box_slice)