code: def _check_data(wavfile, station, channel, debug=0):
      
      if debug > 1:
          print('Checking ' + wavfile)
      st = read(wavfile, headonly=True)
      for tr in st:
          if tr.stats.station == station and tr.stats.channel == channel:
              return wavfile
docs: Inner loop for parallel checks.
  
      :type wavfile: str
      :param wavfile: Wavefile path name to look in.
      :type station: str
      :param station: Channel name to check for
      :type channel: str
      :param channel: Channel name to check for
      :type debug: int
      :param debug: Debug level, if > 1, will output what it it working on.