KeyError: 'f'

[Dogeeeeeee]

I was using my customized COCO dataset to train a new model
I use the command "python train.py CenterNet-52" and I modified relevant configs. but I got this error. could you help me to figure out where the problem is?
loading all datasets...
using 4 threads
loading from cache file: cache/coco_trainval2014.pkl
No cache file found...
loading annotations into memory...
Done (t=0.09s)
creating index...
index created!
Traceback (most recent call last):
File "train.py", line 193, in
training_dbs = [datasets[dataset](configs["db"], train_split) for _ in range(threads)]
File "train.py", line 193, in
training_dbs = [datasets[dataset](configs["db"], train_split) for _ in range(threads)]
File "/content/CenterNet/db/coco.py", line 60, in init
self._load_data()
File "/content/CenterNet/db/coco.py", line 69, in _load_data
self._extract_data()
File "/content/CenterNet/db/coco.py", line 103, in _extract_data
for img_id in coco_image_ids
File "/content/CenterNet/db/coco.py", line 103, in
for img_id in coco_image_ids
File "data/coco/PythonAPI/pycocotools/coco.py", line 229, in loadImgs
return [self.imgs[id] for id in ids]
File "data/coco/PythonAPI/pycocotools/coco.py", line 229, in
return [self.imgs[id] for id in ids]
KeyError: 'f'