code: def ReadMostRecentClientGraphSeries(
        self,
        client_label,
        report_type,
        cursor=None):
      
      query = """
        SELECT graph_series
        FROM client_report_graphs
        WHERE client_label = %s AND report_type = %s
        ORDER BY timestamp DESC
        LIMIT 1
      """
      args = [client_label, report_type.SerializeToDataStore()]
      cursor.execute(query, args)
      result = cursor.fetchone()
      if result is None:
        return None
      else:
        return rdf_stats.ClientGraphSeries.FromSerializedString(result[0])
docs: Fetches the latest graph series for a client-label from the DB.