code: def _FetchMostRecentGraphSeriesFromTheLegacyDB(
      label,
      report_type,
      token = None
  ):
    
    try:
      stats_for_label = aff4.FACTORY.Open(
          GetAFF4ClientReportsURN().Add(label),
          aff4_type=aff4_stats.ClientFleetStats,
          mode="r",
          token=token)
    except aff4.InstantiationError:
      # Nothing to return for the given label and report-type.
      return None
    aff4_attr = _GetAFF4AttributeForReportType(report_type)
    graph_series = rdf_stats.ClientGraphSeries(report_type=report_type)
    if aff4_attr.attribute_type == rdf_stats.GraphSeries:
      graphs = stats_for_label.Get(aff4_attr)
      if graphs is None:
        return None
      for graph in graphs:
        graph_series.graphs.Append(graph)
    elif aff4_attr.attribute_type == rdf_stats.Graph:
      graph = stats_for_label.Get(aff4_attr)
      if graph is None:
        return None
      graph_series.graphs.Append(graph)
    else:
      raise AFF4AttributeTypeError(aff4_attr.attribute_type)
    return graph_series
docs: Fetches the latest graph-series for a client label from the legacy 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 DB.
  
    Raises:
      AFF4AttributeTypeError: If 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.