Were not handling the case where the eval result is None e.g. some columns have a peak value, but it is unused, so we use 'None', which evaluates to the None object. Return empty string in this case.
Were not handling the case where the eval result is None e.g. some columns have a peak value, but it is unused, so we use 'None', which evaluates to the None object. Return empty string in this case.