needs_grad and has_grad not longer work

[ifsheldon]

Describe the bug
field.snode.needs_grad and field.snode.ptr.has_grad do not longer work but my library stannum depends on one of these two to perform checks.

Breaking PRs
#4308 removed field.snode.needs_grad and #5083 removed has_grad from CPP SNode class.

This is not a bug but a breaking change that silently breaks my library. I understand you are preparing for forward differentiation and thus doing a lot of refactoring but I need an API to tell me if a field need gradient or not in the conventional backward mode (because it works with Autograd in PyTorch)

[strongoier]

Hi @ifsheldon. Thanks for reporting this! Does field.snode.ptr.has_adjoint() work for you?

[ifsheldon]

OK, fixed it.