In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Add the background task

emoveAttribute("id")}}}return re(t.replace(ve,"$1"),e,n,r)}function W(){var r=[];return function e(t,n){return r.push(t+" ")>b.cacheLength&&delete e[r.shift()],e[t+" "]=n}}function F(e){return e[S]=!0,e}function $(e){var t=T.createElement("fieldset");try{return!!e(t)}catch(e){return!1}finally{t.parentNode&&t.parentNode.removeChild(t),t=null}}function B(t){return function(e){return fe(e,"input")&&e.type===t}}function _(t){return function(e){return(fe(e,"input")||fe(e,"button"))&&e.type===t}}function...

      extends AbstractTransformFuture<I, O, Function<? super I, ? extends O>, O> {
    TransformFuture(
        ListenableFuture<? extends I> inputFuture, Function<? super I, ? extends O> function) {
      super(inputFuture, function);
    }

    @Override
    @ParametricNullness
    O doTransform(Function<? super I, ? extends O> function, @ParametricNullness I input) {
      return function.apply(input);
    }

    @Override

///

## Other Asynchronous Function Calls

As the testing function is now asynchronous, you can now also call (and `await`) other `async` functions apart from sending requests to your FastAPI application in your tests, exactly as you would call them anywhere else in your code.

/// tip

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.

You can think of it as a *path operation function* without the "decorator" (without the `@app.get("/some-path")`).

n=d.getTransitionDurationFromElement(t);o.default(t).one(d.TRANSITION_END,(function(n){return e._destroyElement(t,n)})).emulateTransitionEnd(n)}else this._destroyElement(t)},e._destroyElement=function(t){o.default(t).detach().trigger("closed.bs.alert").remove()},t._jQueryInterface=function(e){return this.each((function(){var n=o.default(this),i=n.data(c);i||(i=new t(this),n.data(c,i)),"close"===e&&i[e](this)}))},t._handleDismiss=function(t){return function(e){e&&e.preventDefault(),t.close(this)}},l(t,null,[{key:"...

Maybe you need to start a new version, or you just got tired of running it. 🤷

///

### Lifespan function

The first thing to notice, is that we are defining an async function with `yield`. This is very similar to Dependencies with `yield`.

{* ../../docs_src/events/tutorial003.py hl[14:19] *}

The first part of the function, before the `yield`, will be executed **before** the application starts.

lter(t)[0]}function N(e,t,o){if(Array.prototype.findIndex)return e.findIndex(function(e){return e[t]===o});var n=D(e,function(e){return e[t]===o});return e.indexOf(n)}function P(t,o,n){var i=void 0===n?t:t.slice(0,N(t,'name',n));return i.forEach(function(t){t['function']&&console.warn('`modifier.function` is deprecated, use `modifier.fn`!');var n=t['function']||t.fn;t.enabled&&e(n)&&(o.offsets.popper=g(o.offsets.popper),o.offsets.reference=g(o.offsets.reference),o=n(o,t))}),o}function k(){if(!th...

meout((function(){var e=n.default(".preloader");e&&(e.css("height",0),setTimeout((function(){e.children().hide()}),200))}),this._config.preloadDuration)},t._max=function(e){var t=0;return Object.keys(e).forEach((function(a){e[a]>t&&(t=e[a])})),t},t._isFooterFixed=function(){return"fixed"===n.default(De).css("position")},e._jQueryInterface=function(t){return void 0===t&&(t=""),this.each((function(){var a=n.default(this).data(He),i=n.default.extend({},Ae,n.default(this).data());a||(a=new e(n.defau...

emoveAttribute("id")}}}return re(t.replace(ve,"$1"),e,n,r)}function W(){var r=[];return function e(t,n){return r.push(t+" ")>b.cacheLength&&delete e[r.shift()],e[t+" "]=n}}function F(e){return e[S]=!0,e}function $(e){var t=T.createElement("fieldset");try{return!!e(t)}catch(e){return!1}finally{t.parentNode&&t.parentNode.removeChild(t),t=null}}function B(t){return function(e){return fe(e,"input")&&e.type===t}}function _(t){return function(e){return(fe(e,"input")||fe(e,"button"))&&e.type===t}}function...