https://matplotlib.org/gallery/lines_bars_and_markers/fill_between_demo.html
[plotting-error-bars](https://tonysyu.github.io/plotting-error-bars.html)
Plot yerr/xerr as shaded region rather than error bars
**matplotlib.pyplot.fill_betweenx**(y, x1, x2=0, where=None, step=None, hold=None, data=None, **kwargs)¶