* It's possible to have arbitrary trees/levels of dependencies with `yield` and exit steps are handled in the correct order automatically.
    * It works by default in Python 3.7 or above. For Python 3.6, it requires the extra backport dependencies:
        * `async-exit-stack`
        * `async-generator`
    * New docs at [Dependencies with `yield`](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-with-yield/).