/**
 * Legacy version of {@link java.util.function.Function java.util.function.Function}.
 *
 * <p>The {@link Functions} class provides common functions and related utilities.
 *
 * <p>As this interface extends {@code java.util.function.Function}, an instance of this type can be
 * used as a {@code java.util.function.Function} directly. To use a {@code
 * java.util.function.Function} in a context where a {@code com.google.common.base.Function} is

{* ../../docs_src/background_tasks/tutorial001.py hl[1,13] *}

**FastAPI** will create the object of type `BackgroundTasks` for you and pass it as that parameter.

## Create a task function { #create-a-task-function }

Create a function to be run as the background task.

It is just a standard function that can receive parameters.

efineProperty(t,o.key,o)}}function y(t,e){return(y=Object.setPrototypeOf||function(t,e){return t.__proto__=e,t})(t,e)}function h(n){var o=function(){if("undefined"==typeof Reflect||!Reflect.construct)return!1;if(Reflect.construct.sham)return!1;if("function"==typeof Proxy)return!0;try{return Date.prototype.toString.call(Reflect.construct(Date,[],function(){})),!0}catch(t){return!1}}();return function(){var t,e=v(n);return t=o?(t=v(this).constructor,Reflect.construct(e,arguments,t)):e.apply(this,a...

      searchForm: $("#searchForm")
    });
  }

  loadImage = function(img, url, limit) {
    var imgData = new Image();
    $(imgData).on("load", function() {
      $(img).css("background-image", "");
      $(img).attr("src", url);
    });
    $(imgData).on("error", function() {
      if (limit > 0) {
        setTimeout(function() {
          loadImage(img, url, --limit);
        }, IMG_LOADING_DELAY);

    /**
     * Creates a composite function from a collection of functions.
     *
     * @param functions A collection of functions, each taking a String as input and returning a String.
     * @return A function that applies each function in the collection in order until a non-null result is found.
     *         If all functions return null, the composite function returns null.
     *

 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */

      return false;
    }
  });

  $(".table tr[data-href]").each(function() {
    $(this)
      .css("cursor", "pointer")
      .hover(
        function() {
          $(this).addClass("active");
        },
        function() {
          $(this).removeClass("active");
        }
      )
      .click(function() {
        document.location = $(this).attr("data-href");
      });
  });

///

## Other Asynchronous Function Calls { #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

e(e,d),b=42===f.offsetWidth,c.removeChild(e),{matches:b,media:a}}}(a.document)}(this),function(a){"use strict";function b(){u(!0)}var c={};a.respond=c,c.update=function(){};var d=[],e=function(){var b=!1;try{b=new a.XMLHttpRequest}catch(c){b=new a.ActiveXObject("Microsoft.XMLHTTP")}return function(){return b}}(),f=function(a,b){var c=e();c&&(c.open("GET",a,!0),c.onreadystatechange=function(){4!==c.readyState||200!==c.status&&304!==c.status||b(c.responseText)},4!==c.readyState&&c.send(null))};if(...

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

///

### Lifespan function { #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.