docs: def FetchMostRecentGraphSeries(label,
                                 report_type,
                                 token = None
                                ):
    """Fetches the latest graph series for a client label from the DB.
  
    Args:
      label: Client label to fetch data for.
      report_type: rdf_stats.ClientGraphSeries.ReportType to fetch data for.
      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:
      The graph series for the given label and report type that was last
      written to the DB, or None if no series for that label and report-type
      exist.
    """
    if _ShouldUseLegacyDatastore():
      return _FetchMostRecentGraphSeriesFromTheLegacyDB(
          label, report_type, token=token)
  
    return data_store.REL_DB.ReadMostRecentClientGraphSeries(label, report_type)