Function reconstruct 

pub fn reconstruct<I: Index, T: ComplexField>(
    out: MatMut<'_, T>,
    L: MatRef<'_, T>,
    diagonal: DiagRef<'_, T>,
    subdiagonal: DiagRef<'_, T>,
    perm: PermRef<'_, I>,
    par: Par,
    stack: &mut MemStack,
)