/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/fluid/dygraph/base.py in grad(outputs, inputs, grad_outputs, retain_graph, create_graph, only_inputs, allow_unused, no_grad_vars)
626 return core.dygraph_partial_grad(inputs, outputs, grad_outputs,
627 no_grad_vars, place, create_graph,
--> 628 retain_graph, allow_unused, only_inputs)
629
630
RuntimeError: (NotFound) The Op flatten_contiguous_range_grad doesn't have any grad op. If you don't intend calculating higher order derivatives, please set `create_graph` to False.
[Hint: double_grad_node should not be null.] (at /paddle/paddle/fluid/imperative/partial_grad_engine.cc:908)