$ python3 demo.py --debug
[ WARN:0] global /tmp/pip-req-build-ms668fyv/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
Traceback (most recent call last):
File "demo.py", line 219, in
main()
File "demo.py", line 62, in main
pose_estimator = PoseEstimator(img_size=sample_frame.shape[:2])
AttributeError: 'NoneType' object has no attribute 'shape'