Axes.add_artist(a)¶Add an Artist to the axes, and return the artist.
Use add_artist only for artists for which there is no dedicated
"add" method; and if necessary, use a method such as update_datalim
to manually update the dataLim if the artist is to be included in
autoscaling.
If no transform has been specified when creating the artist (e.g.
artist.get_transform() == None) then the transform is set to
ax.transData.
matplotlib.axes.Axes.add_artist¶