What's the difference between 'ann_infos' and 'ann_info' ?????

[finninmunich]

This question is driving me crazy. I noticed that we have both 'ann_infos' and 'ann_info' that can be loaded as gt_bbox_3d. I thought that maybe one is under ego coordiantes and the other is under global/camera coordinates. But after I studied the source code of creating/loading data, I think both gt_bbox_3d is located in ego coordinates. So what's the point of creating 'ann_infos'????? Also, I check the dimension of them under same frame, the number of bboxing is different. How can this happened?