code: def _add_data_line(self, data, col, value, ts):
      
      if col in self.column_csv_map:
        out_csv = self.column_csv_map[col]
      else:
        out_csv = self.get_csv(col)   # column_csv_map[] is assigned in get_csv()
        data[out_csv] = []
      data[out_csv].append(ts + "," + value)
docs: Append the data point to the dictionary of "data"
      :param data: The dictionary containing all data
      :param col: The sub-metric name e.g. 'host1_port1.host2_port2.SendQ'
      :param value: integer
      :param ts: timestamp
      :return: None