'Return the :class:`~matplotlib.transforms.Transform`
instance used by this artist.'

def get_transform(self):

    if (self._transform is None):
        self._transform = IdentityTransform()
    elif ((not isinstance(self._transform, Transform)) and hasattr(self._transform, u'_as_mpl_transform')):
        self._transform = self._transform._as_mpl_transform(self.axes)
    return self._transform
