tensor([[ 2,  3],
              [ 5,  6],
              [ 8,  9]])
      >>> s = torch.arange(16).reshape(2, 2, 2, 2).to_sparse(2)
      >>> torch.narrow_copy(s, 0, 0, 1)
      tensor(indices=tensor([[0, 0],
                             [0, 1]]),
             values=tensor([[[0, 1],
                             [2, 3]],
                        [[4, 5],
                         [6, 7]]]),
         size=(1, 2, 2, 2), nnz=2, layout=torch.sparse_coo)

See also: "torch.narrow()" for a non copy variant