lbft with subhourly data

[MO-marcomilan]

Hi,
I have a script, which works well without time dimension.
For file with time dimension (subhourly every 10 minutes), it doesn't work:

    add_operator = AddFieldsOperator()

    ff_out = ff.copy()

    for field_1 in ff.fields:
        # if stash eq 12 then add 271 to it before writing the data out
        if (field_1.lbrel in (2,3) and field_1.lbuser4 == 12):  #qcf
            for field_2 in ff.fields:
                if ((field_2.lbrel in (2,3) and field_2.lbuser4 == 271) and  #qcf2
                    (field_1.lbft == field_2.lbft) and
                    (field_1.lblev == field_2.lblev)):
                    ff_out.fields.append(add_operator([field_1, field_2])) #qcf+qcf2
                    break

I suppose it is because of the fact that lbft is an integer.
Does someone know a workaround?
Thanks