bars dataset + priors

[alvinzz]

Refactor BarsDataset.

Adds Priors:

• Spike-and-Slab
• L0-norm

Updates unittests.

[belsten]

General comment about formatting, we currently have a formatting style guide that is in another branch and will be merged. https://github.com/rctn/sparsecoding/blob/formatting/docs/contributing.md
Much of the stable code we have right now follows this guide.

[cshewmake2]

Thanks for all of the commits! For future reference: let's make sure each branch is adding its own feature. It's a lot easier to review and accept PRs quickly when they're atomic and add a specific new functionality or change.

[alvinz-matician]

Yeah old (bad) habits die hard. If it's too much I'm happy to break it up into smaller PRs. But it would be difficult to split everything from moving the BarsDataset to the last tests change, since the tests depend on that dataset.

[cshewmake2]

This is cool. What's the difference between having Prior inherit abc.ABC vs just inheriting the default object type implicitly?
e.g.
class Prior(): or class Prior:

Does it just enforce the interface/inheritance structure somehow?

[alvinzz]

It doesn't really enforce anything (being Python and all), but semantically it's designed for this purpose:

https://peps.python.org/pep-3119/

ABCs are simply Python classes that are added into an object’s inheritance tree to signal certain features of that object to an external inspector. Tests are done using isinstance(), and the presence of a particular ABC means that the test has passed.

In addition, the ABCs define a minimal set of methods that establish the characteristic behavior of the type. Code that discriminates objects based on their ABC type can trust that those methods will always be present. Each of these methods are accompanied by an generalized abstract semantic definition that is described in the documentation for the ABC. These standard semantic definitions are not enforced, but are strongly recommended.

[cshewmake2]

I have yet to test out everything on my local machine. Will try to do that tomorrow sometime.

[alvinzz]

Updated to have Numpy-style docstrings & pruned some commits into other PRs.

[ligeralde]

make variable names all explicit (e.g., D --> dimension)