def _split_lobster_filename_core(filename):
    """ splits the LOBSTER-type filename into Ticker, Date, Time Start, Time End, File Type, Number of Levels """
    filename2, _ = filename.split(".")
    ticker_str, date_str, time_start_str, time_end_str, file_type_str, num_levels = filename2.split("_") 
    return ticker_str, date_str, time_start_str, time_end_str, file_type_str, num_levels