def _verify_allowed_order_field(self, order_by: str) -> None:
        """
        Verifies if proper field string is used.
        :param order_by: string with order by definition
        :type order_by: str
        """
        parts = order_by.split("__")
        if len(parts) > 2 or parts[0] != self.target_field.through.get_name():
            raise ModelDefinitionError(
                "You can order the relation only " "by related or link table columns!"
            )

        Verifies if proper field string is used.
        :param order_by: string with order by definition
        :type order_by: str
        
ormar/queryset/join.py