Surface.normal does not support 'tensor' keyword

[VikingScientist]

from splipy import *
import numpy as np

surf = Surface()
t = np.linspace(0,1,10)
x     = surf.evaluate(t,t, tensor=False) # gives output x.shape == [10,10,2]
x     = surf.evaluate(t,t, tensor=True) # gives output x.shape == [10,2]
dx,dy = surf.tangent( t,t, tensor=True) # gives output dx.shape == [10,10,2]
x     = surf.normal(  t,t, tensor=True) # crashes miserably :(