thank you for your reply
the error still occurs.
Traceback (most recent call last):
File “/Users/cc/Downloads/dgl-examples-pytorch/code1211/hgnn/hgnn.py”, line 778, in
main()
File “/Users/cc/Downloads/dgl-examples-pytorch/code1211/hgnn/hgnn.py”, line 699, in main
loss.backward(retain_graph=True)
File “/Users/cc/PycharmProjects/testfolder1127/venvpy3/lib/python3.7/site-packages/torch/tensor.py”, line 166, in backward
torch.autograd.backward(self, gradient, retain_graph, create_graph)
File “/Users/cc/PycharmProjects/testfolder1127/venvpy3/lib/python3.7/site-packages/torch/autograd/ init .py”, line 99, in backward
allow_unreachable=True) # allow_unreachable flag
File “/Users/cc/PycharmProjects/testfolder1127/venvpy3/lib/python3.7/site-packages/torch/autograd/function.py”, line 77, in apply
return self._forward_cls.backward(self, *args)
File “/Users/cc/PycharmProjects/testfolder1127/venvpy3/lib/python3.7/site-packages/dgl/backend/pytorch/tensor.py”, line 336, in backward
= ctx.backward_cache
TypeError: cannot unpack non-iterable NoneType object