presto-parser/src/main/java/io/prestosql/sql/ExpressionFormatter.java/ExpressionFormatter/visitWindowFrame
class ExpressionFormatter:        @Override
        public String visitWindowFrame(WindowFrame node, Void context)
        {
            StringBuilder builder = new StringBuilder();

            builder.append(node.getType().toString()).append(' ');

            if (node.getEnd().isPresent()) {
                builder.append("BETWEEN ")
                        .append(process(node.getStart(), context))
                        .append(" AND ")
                        .append(process(node.getEnd().get(), context));
            }
            else {
                builder.append(process(node.getStart(), context));
            }

            return builder.toString();
        }