'Add any :class:`~matplotlib.artist.Artist` to the axes.
Use `add_artist` only for artists for which there is no dedicated
"add" method; and if necessary, use a method such as
`update_datalim` or `update_datalim_numerix` to manually update the
dataLim if the artist is to be included in autoscaling.
Returns the artist.'

def add_artist(self, a):

    a.axes = self
    self.artists.append(a)
    self._set_artist_props(a)
    a.set_clip_path(self.patch)
    a._remove_method = (lambda h: self.artists.remove(h))
    self.stale = True
    return a
