def save_data(data_list, save_dir='../../data/'):
    """
    Save processed data to csv files

    Parameters
    ----------
    datalist: A list containing pandas dataframes of all sessions' raw data
    save_dir: A path to save files in

    return
    ----------
    Show the result of saving grades, "Saved"
    """
    # Error meassage
    if not isinstance(data_list, list) is True:
        raise ValueError("'data_list' should be a list including panda dataframes.")
    # Save datasets
    for i, session in enumerate(data_list):
        if i == 0:
            continue
        file_name = "variables_session_" + str(i) + "_not_filtered.csv"
        session.to_csv(save_dir + file_name)
    return print("Saved")