code: def validate(self, record, values):
          
          schema = record.schema()
          columns = self.columns()
          try:
              column_values = [values[col] for col in columns]
          except KeyError as err:
              msg = 'Missing {0} from {1}.{2} index'.format(err[0].name(),
                                                            record.schema().name(),
                                                            self.name())
              raise errors.InvalidIndexArguments(self.schema(), msg=msg)
  
          # # ensure a unique record is preserved
          # if self.unique():
          #     lookup = getattr(record, self.name())
          #     other = lookup(*column_values)
          #     if other and other != record:
          #         msg = 'A record already exists with the same {0} combination.'.format(', '.join(self.columnNames()))
          #         raise errors.IndexValidationError(self, msg=msg)
  
          return True
docs: Validates whether or not this index's requirements are satisfied by the inputted record and
          values.  If this index fails validation, a ValidationError will be raised.
  
          :param      record | subclass of <orb.Table>
                      values | {<orb.Column>: <variant>, ..}
  
          :return     <bool>