Code cleanup

ml-agents/mlagents/trainers/optimizer/torch_optimizer.py

             )
 
         # Convert to tensors
-        current_obs = ObsUtil.from_buffer(batch, n_obs)
-        current_obs = [ModelUtils.list_to_tensor(obs) for obs in current_obs]
+        current_obs = [
+            ModelUtils.list_to_tensor(obs) for obs in ObsUtil.from_buffer(batch, n_obs)
+        ]
         next_obs = [ModelUtils.list_to_tensor(obs) for obs in next_obs]
 
         next_obs = [obs.unsqueeze(0) for obs in next_obs]