variables rather than sharing the same variables in each iteration.
</li>
<li>
A "for" statement with <a href="#For_range">"range" clause</a> may iterate over
integer values from zero to an upper limit.
</li>
</ul>

<h3 id="Type_unification_rules">Type unification rules</h3>

<p>
The type unification rules describe if and how two types unify.

    * It's now possible to use the low level utility `iterate_in_threadpool` from `starlette.concurrency` (for advanced scenarios).
    * PR [#243](https://github.com/tiangolo/fastapi/pull/243).