feat: update loss calculation to support 5d tensor

train_network.py

@@ -470,7 +470,7 @@ class NetworkTrainer:
             loss = loss * weighting
         if args.masked_loss or ("alpha_masks" in batch and batch["alpha_masks"] is not None):
             loss = apply_masked_loss(loss, batch)
-        loss = loss.mean([1, 2, 3])
+        loss = loss.mean(dim=list(range(1, loss.ndim)))  # mean over all dims except batch
 
         loss_weights = batch["loss_weights"]  # 各sampleごとのweight
         loss = loss * loss_weights