the step1 logits ：
logits tensor([[ 0.8831, -0.0368, -0.2206, -2.3484, -1.3595]], device=‘cuda:1’,
grad_fn=)
the step1 loss：
tensor(1.5489, device=‘cuda:1’, grad_fn=NllLossBackward>)
but why can’t loss.backward()?