Antarctica data generator always loads PyTorch

[wesselb]

The Antarctica data generator always loads PyTorch, which forces scripts that intend to use only TF to also install Torch or [even causes these scripts to crash]. The data generator should be refactored to be backend-agnostic.

@tom-andersson @stratisMarkou

[tom-andersson]

I suspect this can be closed as this is no longer used? Thoughts @stratisMarkou?

[stratisMarkou]

I am eventually going to use this to run some experiments, but haven't got around to doing this yet.

[tom-andersson]

Okay my bad, no probs :-)