Parameters
    ----------
    folder : str

    Returns
    -------
    list of HandwrittenData objects

def read_folder(folder):
    """
    Parameters
    ----------
    folder : str

    Returns
    -------
    list of HandwrittenData objects
    """
    hwr_objects = []
    for filepath in natsort.natsorted(glob.glob("%s/*.inkml" % folder)):
        tmp = inkml.read(filepath)
        for hwr in tmp.to_single_symbol_list():
            hwr_objects.append(hwr)
    logging.info("Done reading formulas")
    save_raw_pickle(hwr_objects)
    return hwr_objects