The new assertions introduced in https://github.com/Codeception/module-symfony/releases/tag/3.5.0 should be added to the docs.
Did you copy them one by one, or did you find a way to call them directly (i.e. future Symfony assertions will automatically work too)?
Are these the ones we're talking about? https://symfony.com/doc/current/testing.html#testing-the-response-assertions