Dear Stackoverflow community;

recently I have been playing around with the Seaborn heatmap function and I was wondering, whether it is possible to use color lines as secondary axes? To be more specific, I would like to reproduce the following plot, which I know how to do in mathematica, in python:

I have written the following, much simplified example

vals = np.array(['A','B','C','D'])
corrs = np.array([[0, 1, 0.5, 3],[1,0,2,0],[0.5, 2,0, 3],[3,0,3,0]])
ax = sns.heatmap(corrs,xticklabels=vals, yticklabels=vals)
plt.show()

and then tinkered with jointplot trying to get a colored line to appear under the axes ticks, but to no avail. Any help would be very much appreciated!