why I fail when running demo_loftr.py following github

[HUSTNO1WXY]

When run demo.py, What else should I notice?
the error is as following:
Traceback (most recent call last):
File "D:\Anaconda\envs\loftr\lib\site-packages\torch\serialization.py", line 308, in _check_seekable
f.seek(f.tell())
AttributeError: 'NoneType' object has no attribute 'seek'

During handling of the above exception, another exception occurred:

[HUSTNO1WXY]

I copy the code from demo_single_pair in notebooks, but it shows exit 0. why?