message: Relax bounds in Ldl::perm
  Since we can now only use the structure, we can actually remove
  constraints on N.
diff: @@ -138,12 +138,11 @@ impl Ldl {
  pub fn perm<N, I>(&self, mat: CsMatViewI<N, I>) -> PermOwnedI<I>
  where
  I: SpIndex,
  - N: Copy + PartialEq,
  {
  match self.fill_red_method {
  FillInReduction::NoReduction => PermOwnedI::identity(mat.rows()),
  FillInReduction::ReverseCuthillMcKee => {
  - sprs::linalg::reverse_cuthill_mckee(mat).perm
  + sprs::linalg::reverse_cuthill_mckee(mat.structure_view()).perm
  }
  _ => {
  unreachable!(
  