There was existing TF 1.0 code I was trying to extract gradients through (nsynth-wavenet). I spent over 8 hours on it unsuccessfully; I asked for help from a friend at Google who worked on TF and he couldn't figure it out either. I emailed the original author of the code and he acknowledged that he didn't know how to do it either, and he had an old notebook he could dig up that kinda would work with a lot of fixes.