Use of opencv-python-headless

[montanier]

We recently encountered an issue due to the dependency of pycls to opencv-python. From a quick glance at the code, we believe that pycls would perform equally well by using the headless version of opencv:
https://pypi.org/project/opencv-python-headless/

Could the maintainer consider a change from opencv-python to opencv-python-headless in the dependencies?