Is there a python implementation of a Face shape detector?
Dear past version of self. With Deep learning; Convolutional Neural Networks,  This becomes a trivial problem. You can retrain Google's inception V3 Model to classify faces into the the 5 face shapes you mentioned in your question. With Just 500 training images you can attain an accuracy of 98%.
Is there an OpenCV-python, dlib or any python 3 implementation of a face shape detector (diamond, oblong, square)?