}

  public <T extends Readable & Appendable> void testMultiBound() {
    assertAssignable(new TypeToken<List<T>>() {}, new TypeToken<List<? extends Readable>>() {});
    assertAssignable(new TypeToken<List<T>>() {}, new TypeToken<List<? extends Appendable>>() {});
  }

  public void testToGenericType() {

  }

  public <T extends Readable & Appendable> void testMultiBound() {
    assertAssignable(new TypeToken<List<T>>() {}, new TypeToken<List<? extends Readable>>() {});
    assertAssignable(new TypeToken<List<T>>() {}, new TypeToken<List<? extends Appendable>>() {});
  }

  public void testToGenericType() {

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

It declares an optional query parameter `q` as a `str`, and then it just returns it.

Diese können so **tief** verschachtelt sein, wie nötig.

**FastAPI** kümmert sich darum, sie aufzulösen.

## Erste Abhängigkeit, „Dependable“

Sie könnten eine erste Abhängigkeit („Dependable“) wie folgt erstellen:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

Diese deklariert einen optionalen Abfrageparameter `q` vom Typ `str` und gibt ihn dann einfach zurück.

## Segunda dependencia, "dependable" y "dependant"

Luego puedes crear otra función de dependencia (un "dependable") que al mismo tiempo declare una dependencia propia (por lo que también es un "dependant"):

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Centrémonos en los parámetros declarados:

# Security Tools

When you need to declare dependencies with OAuth2 scopes you use `Security()`.

But you still need to define what is the dependable, the callable that you pass as a parameter to `Depends()` or `Security()`.

There are multiple tools that you can use to create those dependables, and they get integrated into OpenAPI so they are shown in the automatic docs UI, they can be used by automatically generated clients and SDKs, etc.

Let's see a very simple example. It will be so simple that it is not very useful, for now.

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

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:

Bevor wir tiefer in das **Dependency Injection** System eintauchen, lassen Sie uns das vorherige Beispiel verbessern.

## Ein `dict` aus dem vorherigen Beispiel

Im vorherigen Beispiel haben wir ein `dict` von unserer Abhängigkeit („Dependable“) zurückgegeben:

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

Aber dann haben wir ein `dict` im Parameter `commons` der *Pfadoperation-Funktion*.

* Release Notes: Release Notes (do not translate to "Notas de la Versión")
* Semantic Versioning: Semantic Versioning (do not translate to "Versionado Semántico")
* dependable: dependable (do not translate to "confiable" or "fiable")
* list (as in Python list): list
* context manager: context manager (do not translate to "gestor de contexto" or "administrador de contexto")
* a little bit: un poquito

## A `dict` from the previous example { #a-dict-from-the-previous-example }

In the previous example, we were returning a `dict` from our dependency ("dependable"):

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

But then we get a `dict` in the parameter `commons` of the *path operation function*.