Multi-class N-pair Loss npair loss 관련 공부자료 : Improved Deep Metric Learning with Multi-class N-pair Loss Objective Examples 참고자료 https://github.com/ChaofWang/Npair_loss_pytorch https://github.com/tensorflow/tensorflow/blob/r1.10/tensorflow/contrib/losses/python/metric_learning/metric_loss_ops.py
