I like this plot, *but* it would be much better to implement this using the ``:plot:`` directive, so we don't have binary files in the repository (and the figure stays up-to-date with future changes to the package).  If you're not familiar with ``:plot:``, see http://matplotlib.org/sampledoc/extensions.html#inserting-matplotlib-plots .  I'd also say you probably want to use ``:include-source:`` so that people reading the documentation understand how they should plot their models.