presto-parser/src/main/java/io/prestosql/sql/ExpressionFormatter.java/ExpressionFormatter/visitWindow
class ExpressionFormatter:        @Override
        public String visitWindow(Window node, Void context)
        {
            List<String> parts = new ArrayList<>();

            if (!node.getPartitionBy().isEmpty()) {
                parts.add("PARTITION BY " + joinExpressions(node.getPartitionBy()));
            }
            if (node.getOrderBy().isPresent()) {
                parts.add(formatOrderBy(node.getOrderBy().get()));
            }
            if (node.getFrame().isPresent()) {
                parts.add(process(node.getFrame().get(), context));
            }

            return '(' + Joiner.on(' ').join(parts) + ')';
        }