def check_valid_timestamp( timestamp=None):
    """Function check_valid_timestamp
    Check for the correct format of string timestamp
    with format <date>_<time>

    :param timestamp: A string timestamp (any format)
    :return bool: True if pattern follows <date>_<time>, otherwise False
    """
    #Check a valid timestamp scheme input
    # <date (YYMMDD)>_<time (hh:mm)>
    ts_valid = False
    if timestamp != None:
        ts = timestamp.split("_")
        if len(ts) == 2 and len(ts[0]) == 6 and len(ts[1]) == 4:
            ts_valid = True

    return ts_valid