def _fix_label_alt_id(table):
    """
    Utility that fixes the 'label_alt_id' column to match what is
    expected in the mmCIF format.

    :param table: pandas DataFrame object
    :return: returns a modified pandas DataFrame
    """
    table['validation_altcode'] = table['validation_altcode'].str.replace(
        '\\ |\\?', '.')
    table['validation_altcode'] = table['validation_altcode'].fillna('.'
        ).astype(str)
    return table
