yolox 训练报错如下代码块：
根据错误提示，在voc.py文件中读取图片时发生异常。
原因：yolox给的源码读取的是lpg格式的图片，而我的输入是png格式的图片，所以报错。
（也有可能是路径没有给正确，无法读取到图片数据）
AssertionError: Caught AssertionError in DataLoader worker process 0.
Original Traceback (most recent call last):
File "/home/crush/ProgramFiles/anaconda3/lib/python3.7/site-packages/torch/utils/data/_utils/worker.py", line 287, in _worker_loop
data = fetcher.fetch(index)
File "/home/crush/ProgramFiles/anaconda3/lib/python3.7/site-packages/torch/utils/data/_utils/fetch.py", line 44, in fetch
data = [self.dataset[idx] for idx in possibly_batched_index]
File "/home/crush/ProgramFiles/anaconda3/lib/python3.7/site-packages/torch/utils/data/_utils/fetch.py", line 44, in
data = [self.dataset[idx] for idx in possibly_batched_index]
File "/home/crush/YOLOX/yolox/data/datasets/datasets_wrapper.py", line 110, in wrapper
ret_val = getitem_fn(self, index)
File "/home/crush/YOLOX/yolox/data/datasets/mosaicdetection.py", line 95, in __getitem__
img, _labels, _, img_id = self._dataset.pull_item(index)
File "/home/crush/YOLOX/yolox/data/datasets/voc.py", line 242, in pull_item
img = self.load_resized_img(index)
File "/home/crush/YOLOX/yolox/data/datasets/voc.py", line 209, in load_resized_img
img = self.load_image(index)
File "/home/crush/YOLOX/yolox/data/datasets/voc.py", line 222, in load_image
assert img is not None
AssertionError
解决：将voc.py文件的120行读取图片代码的jpg格式改为png，错误解决！
#self._imgpath = os.path.join("%s", "JPEGImages", "%s.jpg")
self._imgpath = os.path.join("%s", "JPEGImages", "%s.png")
