KDE backend function documentation missing

[zachjweiner]

The docstring of kde cites kde_linear and kde_circular for details on keyword args, but their docstrings don't appear in the documentation. (Note that both methods actually have leading underscores.)

[zachjweiner]

To make matters worse, the KDE backend functions take arbitrary kwargs (even though none use them) without complaint, so it's basically impossible to know what one can and can't do without locating and then importing the backend method from arviz.stats.density_utils to query its docstring (and also realizing the function name is actually prefixed with an underscore, in contrast to the arviz.kde docstring).

I'm happy to implement a solution if it'd be helpful, if a maintainer can make a decision (whether to change the backend function names or just fix the docstring, on what page to add the backend methods' documentation, etc.).

[OriolAbril]

These should not be private methods but public ones. It would be great if you can make these changes. From the top of my hand you'll need to:

• modify _kde_linear and _kde_circular to be kde_linear and kde_circular
• update imports and kde source to take this into account
• add kde_linear and kde_circular to https://github.com/arviz-devs/arviz/blob/main/doc/source/api/stats.rst
• check if there are tests using either of the modified functions explicitly and update those too

[zachjweiner]

Thanks - I'll try to get to this soon.

Maybe it'd be prudent to try and tackle #2190 at the same time? Let me know what you think.

[OriolAbril]

I'd probably do 2 different PRs, one per issue, but either way should be fine