fix D.optim.zero_grad() typo

Author: ajbrock

train_fns.py

@@ -33,6 +33,7 @@ def train(x, y):
 
     for step_index in range(config['num_D_steps']):
       # If accumulating gradients, loop multiple times before an optimizer step
+      D.optim.zero_grad()
       for accumulation_index in range(config['num_D_accumulations']):
         z_.sample_()
         y_.sample_()