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")`).

    <function-class>org.codelibs.fess.taglib.FessFunctions</function-class>
    <function-signature>java.lang.String mltForm()</function-signature>
    <example>
      ${fe:mltForm()}
    </example>
  </function>

  <function>
    <description>
      Returns a hidden form for Geo.
    </description>
    <name>geoForm</name>
    <function-class>org.codelibs.fess.taglib.FessFunctions</function-class>

import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

Lkotlin/jvm/functions/Function1;
Lkotlin/jvm/functions/Function20;
Lkotlin/jvm/functions/Function21;
Lkotlin/jvm/functions/Function22;
Lkotlin/jvm/functions/Function2;
Lkotlin/jvm/functions/Function3;
Lkotlin/jvm/functions/Function4;
Lkotlin/jvm/functions/Function5;
Lkotlin/jvm/functions/Function6;
Lkotlin/jvm/functions/Function7;
Lkotlin/jvm/functions/Function8;
Lkotlin/jvm/functions/Function9;
Lkotlin/jvm/internal/ArrayIterator;

   *
   * @param function A Function to transform the results of this future to the results of the
   *     returned future.
   * @param executor Executor to run the function in.
   * @return A future that holds result of the transformation.
   */
  public final <T extends @Nullable Object> FluentFuture<T> transform(
      Function<? super V, T> function, Executor executor) {

import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

    new EqualsTester()
        .addEqualityGroup(
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")),
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(2), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("bar")))
        .testEquals();
  }

    new EqualsTester()
        .addEqualityGroup(
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")),
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(2), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("bar")))
        .testEquals();
  }

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_py39.py hl[14:19] *}

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

* `"function"`: startet die Abhängigkeit vor der *Pfadoperation-Funktion*, die den Request bearbeitet, beendet die Abhängigkeit nach dem Ende der *Pfadoperation-Funktion*, aber **bevor** die Response an den Client zurückgesendet wird. Die Abhängigkeitsfunktion wird also **um** die *Pfadoperation-**Funktion*** **herum** ausgeführt.