presto-main/src/main/java/io/prestosql/sql/gen/LambdaExpressionExtractor.java/LambdaExpressionExtractor/extractLambdaExpressions
class LambdaExpressionExtractor:    public static List<LambdaDefinitionExpression> extractLambdaExpressions(RowExpression expression)
    {
        Visitor visitor = new Visitor();
        expression.accept(visitor, new Context(false));
        return visitor.getLambdaExpressionsPostOrder();
    }