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

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

     *
     * @throws NullPointerException if the input collection is null or contains null elements.
     */
    static Function<String, String> chain(Collection<? extends Function<String, String>> functions) {
        return s -> {
            for (Function<String, String> function : functions) {
                String v = function.apply(s);
                if (v != null) {

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:"...

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

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...

      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");
      });
  });

	"net"
	"time"
)

// LookupHost is a function to make custom lookupHost for optional cached DNS requests
type LookupHost func(ctx context.Context, host string) (addrs []string, err error)

// DialContextWithLookupHost is a helper function which returns `net.DialContext` function.
// It randomly fetches an IP via custom LookupHost function and dials it by the given dial

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A hash function is a collision-averse pure function that maps an arbitrary block of data to a
 * number called a <i>hash code</i>.
 *
 * <h3>Definition</h3>
 *
 * <p>Unpacking this definition:
 *
 * <ul>
 *   <li><b>block of data:</b> the input for a hash function is always, in concept, an ordered byte

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A hash function is a collision-averse pure function that maps an arbitrary block of data to a
 * number called a <i>hash code</i>.
 *
 * <h3>Definition</h3>
 *
 * <p>Unpacking this definition:
 *
 * <ul>
 *   <li><b>block of data:</b> the input for a hash function is always, in concept, an ordered byte