'Add a :class:`~matplotlib.patches.Patch` *p* to the list of
axes patches; the clipbox will be set to the Axes clipping
box.  If the transform is not set, it will be set to
:attr:`transData`.
Returns the patch.'

def add_patch(self, p):

    self._set_artist_props(p)
    if (p.get_clip_path() is None):
        p.set_clip_path(self.patch)
    self._update_patch_limits(p)
    if (self.name != u'rectilinear'):
        path = p.get_path()
        path._interpolation_steps = max(path._interpolation_steps, 100)
    self.patches.append(p)
    p._remove_method = (lambda h: self.patches.remove(h))
    return p
