How to change input "id" in FormType.php Symfony 4

I have tried to change the attr "id" in a FormType.php file :

->add('content', TextareaType::class,(['label' => "Description détaillée",'attr' => ['placeholder' => "Donnez une description qui donne vraiment envoe de venir chez vous !",'id' => "test_id"     ]]))

I only want to change the "ID". How can I do?