calc_off_diag_guga_ref_direct Function

    function calc_off_diag_guga_ref_direct(ilut, csf_i, run, exlevel) result(hel)
        integer(n_int), intent(in) :: ilut(0:niftot)
        type(CSF_Info_t), intent(in) :: csf_i
        integer, intent(in), optional :: run
        integer, intent(out), optional :: exlevel
        HElement_t(dp) :: hel

        integer :: run_
        type(ExcitationInformation_t) :: excitInfo

        def_default(run_, run, 1)
        call calc_guga_matrix_element(ilut, csf_i, ilutRef(0:niftot, run_), csf_ref(run_), excitInfo, hel, .true.)

        if (present(exlevel)) then
            if (excitInfo%valid) then
                exlevel = merge(1, 2, excitInfo%typ == excit_type%single)
            else
                ! non-valid > 3 excit
                exlevel = nel
            end if
        end if
    end function calc_off_diag_guga_ref_direct