presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitLambda
class AstBuilder:    @Override
    public Node visitLambda(SqlBaseParser.LambdaContext context)
    {
        List<LambdaArgumentDeclaration> arguments = visit(context.identifier(), Identifier.class).stream()
                .map(LambdaArgumentDeclaration::new)
                .collect(toList());

        Expression body = (Expression) visit(context.expression());

        return new LambdaExpression(getLocation(context), arguments, body);
    }