message: TF: Fix comment.
  I was looking for the gradient of this function but couldn't find _CrossEntropyGrad method anywhere. CrossEntropyGrad in nn_grad.cc is the closest thing that I can find.
diff: @@ -3299,7 +3299,7 @@ def softmax_cross_entropy_with_logits_v2_helper(
  # Do the actual op computation.
  # The second output tensor contains the gradients. We use it in
  - # _CrossEntropyGrad() in nn_grad but not here.
  + # CrossEntropyGrad() in nn_grad but not here.
  cost, unused_backprop = gen_nn_ops.softmax_cross_entropy_with_logits(
  precise_logits, labels, name=name)
  