AssertionError: Caught AssertionError in DataLoader worker process 0.

I train my own datasets with coco format
and I check my data path
I put my data in "YOLOX/datastes/COCO"
COCO includes:
annotations
train2017
val2017

and I see another people have the same issue , but I still can't solute this problems.

Best Regards,
thank you

AssertionError: Caught AssertionError in DataLoader worker process 0.
Original Traceback (most recent call last):
File "/home/u1764740/.local/lib/python3.6/site-packages/torch/utils/data/_utils/worker.py", line 287, in _worker_loop
data = fetcher.fetch(index)
File "/home/u1764740/.local/lib/python3.6/site-packages/torch/utils/data/_utils/fetch.py", line 49, in fetch
data = [self.dataset[idx] for idx in possibly_batched_index]
File "/home/u1764740/.local/lib/python3.6/site-packages/torch/utils/data/_utils/fetch.py", line 49, in
data = [self.dataset[idx] for idx in possibly_batched_index]
File "/home/u1764740/train/YOLOX/yolox/data/datasets/datasets_wrapper.py", line 110, in wrapper
ret_val = getitem_fn(self, index)
File "/home/u1764740/train/YOLOX/yolox/data/datasets/coco.py", line 235, in getitem
img, target, img_info, img_id = self.pull_item(index)
File "/home/u1764740/train/YOLOX/yolox/data/datasets/coco.py", line 211, in pull_item
img = self.load_resized_img(index)
File "/home/u1764740/train/YOLOX/yolox/data/datasets/coco.py", line 179, in load_resized_img
img = self.load_image(index)
File "/home/u1764740/train/YOLOX/yolox/data/datasets/coco.py", line 199, in load_image
assert img is not None
AssertionError

Start with yolox/data/datasets/coco.py at load_image, where the assertion occurs, and trace the dataset path and image loading used by pull_item. Verify the reported COCO directory layout and determine why an image is unavailable; done means the dataset loads without the DataLoader assertion.