Fix neural style transfer scripmodule creation script error (#48)

Author: mfl28

tutorials/advanced/neural_style_transfer/model/create_vgg19_layers_scriptmodule.py

@@ -9,9 +9,13 @@ def main():
     for param in vgg_19_layers.parameters():
         param.requires_grad = False
 
+    example = torch.rand(1, 3, 224, 224)
+
+    traced_script_module = torch.jit.trace(vgg_19_layers, example)
+
     # Serialize scriptmodule to a file.
     filename = "vgg19_layers.pt"
-    vgg_19_layers.save(filename)
+    traced_script_module.save(filename)
     print(f"Successfully created scriptmodule file {filename}.")