code: def airplane(self, model_mask: str = '###') -> str:
          
          model = self.random.custom_code(mask=model_mask)
          plane = self.random.choice(AIRPLANES)
          return '{} {}'.format(plane, model)
docs: Generate a dummy airplane model.
  
          :param model_mask: Mask of truck model. Here '@' is a
              placeholder of characters and '#' is a placeholder of digits.
          :return: Airplane model.
  
          :Example:
              Boeing 727.