def process_designate_subpart(amendment):
    """ Process the designate amendment if it adds a subpart. """

    if 'Subpart' in amendment.destination:
        subpart_changes = {}

        for label in amendment.labels:
            label_id = '-'.join(label)
            subpart_changes[label_id] = {
                'action': 'DESIGNATE', 'destination': amendment.destination}
        return subpart_changes