Limiting the version of the opencv-python in requirements.txt

[JosenJiang]

Python=3.6 && opencv-python=4.7.0.72
It will raise error "cv2.error: OpenCV(4.7.0) /tmp/pip-install-nzi856ln/opencv-python_f33732a96f0e44e08ea9072d768bb35d/opencv/modules/highgui/src/window.cpp:1272: error: (-2:Unspecified error) The function is not implemented."

I reinstall opencv-python=4.4.0.46, then the error dose not occur. So I recommend limiting the version of the opencv-python in requirements.txt.