ValueError: No variables to optimize

[RichardChen123]

I'm trying to run the command given in the readme to train the DAGAN. At first, I had to fix some compatibility issues between tensorflow versions 1.x and 2.9.1 such as tf_slim instead of tf.contrib and using keras layers. It compiles now, but during runtime, I get the error "No variables to optimize" in the train() method of dagan_networks_wgan.py on the following line:
opt_ops["g_opt_op"] = opts["g_opt"].minimize(losses["g_losses"],
var_list=self.g.variables,
colocate_gradients_with_ops=True)

It seems like there are no variables in the graph during the first time the train function is called? Has anyone gotten this to work in recent tensorflow versions?