-f https://download.pytorch.org/whl/torch_stable.html
torch == 1.7.1+cpu; sys_platform != 'darwin'
torchvision == 0.8.2+cpu; sys_platform != 'darwin'

torch <= 1.7.1; sys_platform == 'darwin'
torchvision == 0.8.2; sys_platform == 'darwin'
