Update tests/test_messagepassing/test_deep_tensor_network_block.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: GiovanniCanali

tests/test_messagepassing/test_deep_tensor_network_block.py

@@ -56,4 +56,4 @@ def test_backward():
 
     loss = torch.mean(output_)
     loss.backward()
-    assert x._grad.shape == x.shape
+    assert x.grad.shape == x.shape