Slice Of A Variable Returns Gradient None

I've been playing around with the tf.gradients() function and came across a behavior I didn't expect. Namely it seems to be unable to calculate the gradient of a sliced Variable. I

Solution 1:

d = c[:, ] creates a different tensor then a, b, c. If you consider dependency graph, d depends on c. then gradients doesn't work in this case. grad(y, x) works if x depends on y, not the other way around.