识别图片过程中调用了Predictor中的postprocess获取的结果转成了json字符串，获取结果如下，其中WordIndex具体含义是什么，希望有个准确的描述：
{"confidence":0.9617134,"label":"334","points":[{"x":30,"y":44},{"x":351,"y":44},{"x":351,"y":197},{"x":30,"y":197}],"wordIndex":[93,93,631]},"wordIndex":[93,93,631]},{"confidence":0.91871727,"label":"下午","points":[{"x":348,"y":97},{"x":423,"y":97},{"x":423,"y":137},{"x":348,"y":137}],"wordIndex":[172,1674]}