'Puts a TransformedPath instance at self._transformed_path;
all invalidation of the transform is then handled by the
TransformedPath instance.'

def _transform_path(self, subslice=None):

    if (subslice is not None):
        xy = STEP_LOOKUP_MAP[self._drawstyle](*self._xy[subslice, :].T)
        _path = Path(np.asarray(xy).T, _interpolation_steps=self._path._interpolation_steps)
    else:
        _path = self._path
    self._transformed_path = TransformedPath(_path, self.get_transform())
