def _get_timespan(self, in_seconds=False): if len(self): timespan_ = self[0]._get_timespan(in_seconds=in_seconds) start_offset = timespan_.start_offset timespan_ = self[-1]._get_timespan(in_seconds=in_seconds) stop_offset = timespan_.stop_offset else: start_offset = Duration(0) stop_offset = Duration(0) return Timespan( start_offset=start_offset, stop_offset=stop_offset, )