presto-main/src/main/java/io/prestosql/sql/gen/LambdaExpressionExtractor.java/Visitor/visitLambda
class Visitor:        @Override
        public Void visitLambda(LambdaDefinitionExpression lambda, Context context)
        {
            lambda.getBody().accept(this, new Context(true));
            lambdaExpressions.add(lambda);
            return null;
        }