Supervised Metric Pretraining

[chingisooinar]

Hello,
I am writing from my first account. I would like to add an option for supervised metric pretraining. It is used with LinearAverage from LinearAverage.py since the output is expected to be passed to this class. It performs eq. (4) as mentioned in https://arxiv.org/pdf/1812.08781.pdf. Also, I found using the temperature parameter handy, as mentioned in https://arxiv.org/pdf/1805.01978.pdf. Thanks for your consideration.

[ghost]

All CLA requirements met.

[bl0]

Thanks a lot for your work. But maybe you should address the following two concerns before the PR is merged.

1. You should reformat the code to make it clean.
2. Maybe you should make it runnable.

[chingisooinar]

Thank you, I refactored it and included a sample code for imagenet dataset.

[bl0]

Thanks a lot for your quick reply.
Can you post the training and finetuning log of the sample code? I want to check the correctness and performance.