def summary_records(self):
        """Yield (record_number, n_summaries, record_data) for each record.

        Readers will only use the second two values in each tuple.
        Writers can update the record using the `record_number`.

        """
        record_number = self.fward
        unpack = self.summary_control_struct.unpack
        while record_number:
            data = self.read_record(record_number)
            next_number, previous_number, n_summaries = unpack(data[:24])
            yield record_number, n_summaries, data
            record_number = int(next_number)
Yield (record_number, n_summaries, record_data) for each record.

        Readers will only use the second two values in each tuple.
        Writers can update the record using the `record_number`.