^I get that error with just `tangent.grad(np.sin)`. So, it's not a nested differentiation problem, so much as a problem with "ufuncs". If you wrap np.sin in yo

^I get that error with just `tangent.grad(np.sin)`. So, it's not a nested differentiation problem, so much as a problem with "ufuncs". If you wrap np.sin in your own function then it takes the gradient just fine. def sin(x): return np.sin(x) negative_sin = tangent.grad(tangent.grad(sin))