(self)
| 119 | super().__init__('R', 'R', data_type, fields) |
| 120 | |
| 121 | def textual_form(self): |
| 122 | # only surface relation is reserved |
| 123 | assert self.depth == 1 |
| 124 | return self.textual_form_core() |
| 125 | |
| 126 | def textual_form_core(self): |
| 127 | return self.fields[0].textual_form() + ' by' |