def _check_data(wavfile, station, channel, debug=0):
    """
    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.
    """
    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
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.