Add direction and direction_neuron objectives

[ndey96]

Hi @greentfrapp,

Thanks so much for making this repo! It has been a great help for me. For my use-case I needed the direction and direction_neuron objectives so I added them into lucent. I also included two demo files but let me know if they should be rolled into a docstring instead. This PR also lays the groundwork to reproduce the activation atlas notebooks from lucid. Would love to hear your thoughts :)

[greentfrapp]

Thank you @ndey96 for the contribution and I'm really glad that you found the library helpful!

The new direction objectives look good! Just a few quick things

• Instead of the demo scripts, add a few key lines in the docstring for the new functions e.g.

  # with resnet18 (possible to change this for inceptionv1? since that's what most of our demos are based on by default)
  direction = torch.rand(256) * 1000 
  obj = objectives.direction(layer='layer3', direction=direction)

• Remove the docstring chunk for direction_neuron that starts with "Defaults to the center neuron." and point the reader to the same docstring chunk in the neuron objective
• Add your new tests at the end of test_objectives.py instead, since some of the tests are kinda sensitive to the random seed

We should be good to merge after that!

[ndey96]

@greentfrapp Addressed your comments :) I noticed that a few other PRs were recently merged. Is it possible to bump the version on PyPI once this gets merged?

Thanks!

[greentfrapp]

Awesome thank you @ndey96 I'll be merging this!

Yes, bumping the pip version is definitely on my personal ToDo list! Well the ToDo list is worryingly long, but I'm feeling a tiny bit more productive this week so I have hope that it will be bumped by the end of the week. Fingers crossed!