docs: def FetchAllGraphSeries(
      label,
      report_type,
      period = None,
      token = None
  ):
    """Fetches graph series for the given label and report-type from the DB.
  
    Args:
      label: Client label to fetch data for.
      report_type: rdf_stats.ClientGraphSeries.ReportType to fetch data for.
      period: rdfvalue.Duration specifying how far back in time to fetch data. If
        not provided, all data for the given label and report-type will be
        returned.
      token: ACL token to use for reading from the legacy (non-relational)
        datastore.
  
    Raises:
      AFF4AttributeTypeError: If, when reading to the legacy DB, an unexpected
      report-data type is encountered.
  
    Returns:
      A dict mapping timestamps to graph-series. The timestamps
      represent when the graph-series were written to the datastore.
    """
    if _ShouldUseLegacyDatastore():
      return _FetchAllGraphSeriesFromTheLegacyDB(
          label, report_type, period=period, token=token)
  
    if period is None:
      time_range = None
    else:
      range_end = rdfvalue.RDFDatetime.Now()
      time_range = time_utils.TimeRange(range_end - period, range_end)
    return data_store.REL_DB.ReadAllClientGraphSeries(
        label, report_type, time_range=time_range)