mu_test = torch.nn.Parameter(torch.zeros(len(Y_test), 2))
 mu_full = torch.cat([mu_train.detach().clone(), mu_test])

I only want to compute gradients for mu_test part of mu_full -> is that possible to do?
torch.cat() returns a tensor and if I wrap the whole thing as a parameter then I guess it has requires_grad=True for the whole tensor.