Add Gradient Visualization on models

[sowmen]

I was trying GradCam implementation from this repo on EfficientNet https://github.com/jacobgil/pytorch-grad-cam but could not make it work with. Size mismatch error occurs in the last layer.

How about adding functionality for GradCam, GuidedBackprop, and other similar gradient visualization methods for the models.

[rwightman]

@sowmen not on my list of things todo, but open to contributions

[Stephenfang51]

looking forward to this func implemented

[sowmen]

looking forward to this func implemented

@Stephenfang51 There's a pytorch library called Captum. It contains many model visualization algorithms and works with all the models from this repo. Give that a try.