def METHOD_NAME(self):
    #asking an h5 object for its name is a slow operation
    idToName = {self._file['null_payload'].id: None}
    for d in self._dataProducts:
        idToName.update(d.idToPayloadNames())
    first = self._group['first'][()]
    last = self._group['last'][()]
    payloadRefs = self._group['payload']
    return list(zip( (IOVSyncValue(x['high'],x['low']) for x in first),
                     (IOVSyncValue(x['high'],x['low']) for x in last),
                     ([idToName[self._file[r].id] for r in refs] for refs in payloadRefs)) )