code: def _retrieve_metadata(stream, channel_name):
          
          lalframe.FrStreamGetVectorLength(channel_name, stream)
          channel_type = lalframe.FrStreamGetTimeSeriesType(channel_name, stream)
          create_series_func = _fr_type_map[channel_type][2]
          get_series_metadata_func = _fr_type_map[channel_type][3]
          series = create_series_func(channel_name, stream.epoch, 0, 0,
                              lal.ADCCountUnit, 0)
          get_series_metadata_func(series, stream)
          return channel_type, int(1.0/series.deltaT)
docs: Retrieve basic metadata by reading the first file in the cache
  
          Parameters
          ----------
          stream: lal stream object
              Stream containing a channel we want to learn about
          channel_name: str
              The name of the channel we want to know the dtype and sample rate of
  
          Returns
          -------
          channel_type: lal type enum
              Enum value which indicates the dtype of the channel
          sample_rate: int
              The sample rate of the data within this channel