==================
for tuple expression
==================

foo = [for v in ["a", "b"]: v]

---

(config_file 
  (body 
    (attribute 
      (identifier) 
      (expression 
        (expr_term 
          (for_expr 
            (for_tuple_expr 
              (for_intro 
              (identifier) 
              (expression 
                (expr_term 
                  (collection_value 
                    (tuple 
                      (expression (expr_term (literal_value (string_lit)))) 
                      (expression (expr_term (literal_value (string_lit)))))))))
              (expression (expr_term (variable_expr (identifier)))))))))))