presto-main/src/main/java/io/prestosql/sql/planner/planprinter/PlanPrinter.java/PlanPrinter/formatFrame
class PlanPrinter:    private static String formatFrame(WindowNode.Frame frame)
    {
        StringBuilder builder = new StringBuilder(frame.getType().toString());

        frame.getOriginalStartValue().ifPresent(value -> builder.append(" ").append(value));
        builder.append(" ").append(frame.getStartType());

        frame.getOriginalEndValue().ifPresent(value -> builder.append(" ").append(value));
        builder.append(" ").append(frame.getEndType());

        return builder.toString();
    }