ridgeline-/joyplots plotting routine

 JoyPy is a one-function Python package based on matplotlib + pandas
 with a single purpose: drawing joyplots (a.k.a. ridgeline plots).
 Joyplots are stacked, partially overlapping density plots.
 They are a nice way to plot data to visually compare distributions,
 especially those that change across one dimension (e.g., over time).
 Though hardly a new technique, they have become very popular lately
 thanks to the R packages ggridges and ggjoy.