presto-parser/src/main/java/io/prestosql/sql/ExpressionFormatter.java/ExpressionFormatter/formatSortItems
class ExpressionFormatter:    private static String formatSortItems(List<SortItem> sortItems)
    {
        return Joiner.on(", ").join(sortItems.stream()
                .map(sortItemFormatterFunction())
                .iterator());
    }