IBP banding data system: Internal maintenance specification

Because blank input fields were represented as None, in that case we return a blank wing field. All actual values are represented by a WingField item, whose .wing field is an integer.

# - - -   W i n g F i e l d . f l a t t e n   - - -

    @staticmethod
    def flatten(wingField):
        '''Flatten a wing field.
        '''
        if  wingField is None:
            return BLANK_WING
        else:
            return "%*d" % (WING_L, wingField.value)