```

    as it will use that `None` as the default value, and that way make the parameter **not required**.

    The `Union[str, None]` part allows your editor to provide better support, but it is not what tells FastAPI that this parameter is not required.

Then, we can pass more parameters to `Query`. In this case, the `max_length` parameter that applies to strings:

```Python

To configure them, pass the `swagger_ui_parameters` argument when creating the `FastAPI()` app object or to the `get_swagger_ui_html()` function.

`swagger_ui_parameters` receives a dictionary with the configurations passed to Swagger UI directly.

        val packageName: Property<String>
        val destDir: DirectoryProperty
    }

    override fun execute() {
        val packageName = parameters.packageName.get()
        val sourceRootDirectory = parameters.destDir.get()
        val packageNamePath = packageName.replace(".", File.separator)
        val packageDirectory = sourceRootDirectory.file(packageNamePath).asFile

If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a *path operation function*. Including sub-dependencies.

That also applies to callables with no parameters at all. The same as it would be for *path operation functions* with no parameters.

**FastAPI** takes advantage of these type hints to do several things.

With **FastAPI** you declare parameters with type hints and you get:

* **Editor support**.
* **Type checks**.

...and **FastAPI** uses the same declarations to:

* **Define requirements**: from request path parameters, query parameters, headers, bodies, dependencies, etc.
* **Convert data**: from the request to the required type.

        </parameter>
        <parameter>
          <name>repositories</name>
          <type>java.util.List</type>
          <required>true</required>
          <editable>false</editable>
        </parameter>
        <parameter>
          <name>resourceBundles</name>
          <type>java.util.List</type>
          <required>true</required>
          <editable>true</editable>
        </parameter>
        <parameter>

* The alternative documentation will also reflect the new query parameter and body:

![ReDoc](https://fastapi.tiangolo.com/img/index/index-06-redoc-02.png)

### Recap

In summary, you declare **once** the types of parameters, body, etc. as function parameters.

You do that with standard modern Python types.

# Dependencies - `Depends()` and `Security()`

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

 themselves:

+-----+
<plugins>
  <plugin>
   <id>xdoc</id>
   <version>1.0</version>
   <parameters>
     <parameter>
       <name>theme</name>
       <value>classic</value>
     </parameter>
   </parameters>
  </plugin>
</plugins>
+-----+

Unified source directory

 Unified source directory structure that is analogous to the repository

        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="1"
    {!> ../../../docs_src/request_forms_and_files/tutorial001.py!}
    ```

## Define `File` and `Form` parameters

Create file and form parameters the same way you would for `Body` or `Query`:

=== "Python 3.9+"

    ```Python hl_lines="10-12"
    {!> ../../../docs_src/request_forms_and_files/tutorial001_an_py39.py!}
    ```