def label_objectness_ignore(label_objectness, iou_above_thresh_indices):
# 注意：这里不能简单的使用 label_objectness[iou_above_thresh_indices] = -1，
# 这样可能会造成label_objectness为1的点被设置为-1了
# 只有将那些被标注为0，且与真实框IoU超过阈值的预测框才被标注为-1
negative_indices = (label_objectness < 0.5)
ignore_indices = negative_indices * iou_above_thresh_indices
label_objectness[ignore_indices] = -1
return label_objectness

请问怎么理解ignore_indices = negative_indices * iou_above_thresh_indices？