default String getSortMetaAsString() {
        return getActiveSortMeta().values().stream()
                .map(SortMeta::getColumnKey)
                .collect(Collectors.joining("','", "['", "']"));
    }
Returns actives sort meta. See {@link SortMeta#compareTo(SortMeta)}
@return map with {@link SortMeta#getField()} as key and {@link SortMeta} as value
primefaces/src/main/java/org/primefaces/component/api/UITable.java