presto-parser/src/main/java/io/prestosql/sql/ExpressionFormatter.java/Formatter/visitIntervalLiteral
class Formatter:        @Override
        protected String visitIntervalLiteral(IntervalLiteral node, Void context)
        {
            String sign = (node.getSign() == IntervalLiteral.Sign.NEGATIVE) ? "- " : "";
            StringBuilder builder = new StringBuilder()
                    .append("INTERVAL ")
                    .append(sign)
                    .append(" '").append(node.getValue()).append("' ")
                    .append(node.getStartField());

            if (node.getEndField().isPresent()) {
                builder.append(" TO ").append(node.getEndField().get());
            }
            return builder.toString();
        }