How to use slices with an accessor in libtorch?

I want to update a 2-dimensional slice of a 3D tensor in libtorch.

I have made an accessor for this 3D tensor.

  1. Would it be quicker to use the accessor to populate the 2D slice? Rather than doing what I was doing up until now, i.e.: Psi_spec.index_put_( {i, Slice(), Slice()}, zero_imag_tensor );

  2. If this is the case, how shall use the accessor to obtain what I obtain with the code above at 1. ?
    Psi_spec_acc.index_put_( {i, Slice(), Slice()}, zero_imag_tensor ); fails.
    Similarly, Psi_spec_acc[i] = zero_imag_tensor; fails as well.
    Moreover, Psi_spec_acc[i][][] = zero_imag_tensor; fails again.

For completeness:
torch::Tensor zero_imag_tensor = torch::zeros( {1}, torch::TensorOptions().dtype(torch::kComplexDouble) );