'Get the axes bounding box in display space.
Subclasses should override for inclusion in the bounding box
"tight" calculation. Default is to return an empty bounding
box at 0, 0.
Be careful when using this function, the results will not update
if the artist window extent of the artist changes.  The extent
can change due to any changes in the transform stack, such as
changing the axes limits, the figure size, or the canvas used
(as is done when saving a figure).  This can lead to unexpected
behavior where interactive figures will look fine on the screen,
but will save incorrectly.'

def get_window_extent(self, renderer):

    return Bbox([[0, 0], [0, 0]])
