def METHOD_NAME(self):
    depth = 0
    condition = self
    while condition.parent_permit_condition_id is not None:
        condition = condition.parent
        depth += 1
    step_format = depth % 3
    if step_format == 0:
        return str(self.display_order) + '.'
    elif step_format == 1:
        return num_to_letter(self.display_order) + '.'
    elif step_format == 2:
        return num_to_roman(self.display_order) + '.'