!!! info
    The `app.webhooks` object is actually just an `APIRouter`, the same type you would use when structuring your app with multiple files.

Notice that with webhooks you are actually not declaring a *path* (like `/items/`), the text you pass there is just an **identifier** of the webhook (the name of the event), for example in `@app.webhooks.post("new-subscription")`, the webhook name is `new-subscription`.

For example, in this application we don't use FastAPI's integrated functionality to extract the JSON Schema from Pydantic models nor the automatic validation for JSON. In fact, we are declaring the request content type as YAML, not JSON:

=== "Pydantic v2"

    ```Python hl_lines="17-22  24"
    {!> ../../../docs_src/path_operation_advanced_configuration/tutorial007.py!}
    ```

    {!> ../../../docs_src/body/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="7-11"
    {!> ../../../docs_src/body/tutorial001.py!}
    ```

The same as when declaring query parameters, when a model attribute has a default value, it is not required. Otherwise, it is required. Use `None` to make it just optional.

For example, this model above declares a JSON "`object`" (or Python `dict`) like:

In some cases you don't really need the return value of a dependency inside your *path operation function*.

Or the dependency doesn't return a value.

But you still need it to be executed/solved.

For those cases, instead of declaring a *path operation function* parameter with `Depends`, you can add a `list` of `dependencies` to the *path operation decorator*.

## Add `dependencies` to the *path operation decorator*

## Changing the default

## Additional media types for the main response

You can use this same `responses` parameter to add different media types for the same main response.

For example, you can add an additional media type of `image/png`, declaring that your *path operation* can return a JSON object (with media type `application/json`) or a PNG image:

```Python hl_lines="19-24  28"
{!../../../docs_src/additional_responses/tutorial002.py!}
```

!!! note

                std::unique_ptr<GradientFunction>* gradient_function) const;

 private:
  absl::flat_hash_map<string, GradientFunctionFactory> registry_;
};

// TODO(srbs): Figure out if we can avoid declaring this in the public header.
// Wrapper for a tensor output of an operation executing under a tape.
//
// `GetID` returns a unique id for the wrapped tensor which is used to maintain

It used custom types in its declarations instead of standard Python types, but it was still a huge step forward.

It also was one of the first frameworks to generate a custom schema declaring the whole API in JSON.

It was not based on a standard like OpenAPI and JSON Schema. So it wouldn't be straightforward to integrate it with other tools, like Swagger UI. But again, it was a very innovative idea.

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="22"
    {!> ../../../docs_src/dependencies/tutorial005.py!}
    ```

!!! info
    Notice that we are only declaring one dependency in the *path operation function*, the `query_or_cookie_extractor`.

        assertThat(projects, hasItem(pluginProject));
        assertThat(projects, hasItem(pluginLevelDepProject));

        // the declaring project MUST be listed after the plugin and its plugin-level dep, though.
        assertEquals(declaringProject, projects.get(3));
    }

    @Test