Does this line of code mess with the ordering in MD plots?

[DanielRPhillips]

Brad McClung has been generating the gsum diagnostics for the order-by-order coefficients in Wolfenstein amplitudes. He had some odd results with MD^2s not being consistent with the PC decomposition. We think we found that this line of code was switching around the sequence of the orders in the MD^2 plots, causing them to be mislabeled and miscolored.

gsum/gsum/diagnostics.py

Line 447 in 05d81ec

positions = positions[inv]

[DanielRPhillips]

Maybe the most useful thing is to explain to us what this line of code is meant to do and why we shouldn't just take the ordering of the points that comes from seaborn's swarmplot.