CodeCat

### 问题确认 Search before asking - [x] 我已经查询[历史issue](https://github.com/PaddlePaddle/PaddleDetection/issues)，没有发现相似的bug。I have searched the [issues](https://github.com/PaddlePaddle/PaddleDetection/issues) and found no similar bug report. ### Bug组件 Bug Component [PaddleDetection](https://github.com/PaddlePaddle/PaddleDetection/tree/release/2.8.1)/[ppdet](https://github.com/PaddlePaddle/PaddleDetection/tree/release/2.8.1/ppdet)/[data](https://github.com/PaddlePaddle/PaddleDetection/tree/release/2.8.1/ppdet/data)/[source](https://github.com/PaddlePaddle/PaddleDetection/tree/release/2.8.1/ppdet/data/source) /dataset.py ### Bug描述 Describe the Bug ```...