Easy Finetuning and Inference

[robinnarsinghranabhat]

Contribution of this PR:

• Support while finetuning Deformable-DETR on custom-data. Checkout : how_to.md
• Provided a Inference Notebook
• Following Error : ImportError:` cannot import name '_NewEmptyTensorOp' from 'torchvision.ops.misc'
• Additional guidelines for easy setup for gcloud gpu instance.

[robinnarsinghranabhat]

Potentially relevant to the following issues:
#49
#97
#117
#116

[nikhilchh]

Hey @robinnarsinghranabhat
I was trying to find the inference notebook but couldn't find it in your repo. Can you point me to that please. Thanks :)

[nikhilchh]

In deformable-DETR code they don't add extra +1 for background because of loss has been designed. (There are some discussions about it in the other issues). But you have mentioned to add +1 in your instruction for fine tuning.

[nhattan417]

More information at: #78 and #72.
(TL;DR due to the difference between Softmax+CE and Sigmoid+BCE)