code: def rename(self):
          
          params = self.relation_name ^ (Optional(self.relation_name) +
                                         self.parenthesize(self.attribute_list))
          return self.parametrize(self.syntax.rename_op, params)
docs: rename_expr ::= rename param_start rename_parameters param_stop
              expression
  
          rename_parameters ::= relation_name |
              paren_left attribute_list paren_right |
              relation_name paren_left attribute_list paren_right