[opt.step](https://docs.pytorch.org/docs/stable/generated/torch.optim.SGD.html#torch.optim.SGD.step "torch.optim.SGD.step")()
[opt.zero_grad](https://docs.pytorch.org/docs/stable/generated/torch.optim.SGD.html#torch.optim.SGD.zero_grad "torch.optim.SGD.zero_grad")()