Why `curl` in `build_test_model` rather than `jacobian3`?

[vivanov879]

Hi @byungsook. In the build_test_model function, curl is used:

            self.G_ = curl(self.G_s)

while in build_model method, jacobian3 is called:

            _, self.G_ = jacobian3(self.G_s)

why is it so? I am looking to advect the model predictions in order to obtain files in .vdb format. Thus, I plan to use jacobian3 call just like when training, and then use the advect method from smoke3_vel_buo.py script.