///

This will let **FastAPI** know that this parameter is required.

### Required, can be `None`

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but still use `...` as the default:

//// tab | Python 3.10+

```Python hl_lines="9"

* Many PRs don't have tests, you can **remind** them to add tests, or you can even **suggest** some tests yourself. That's one of the things that consume most time and you can help a lot with that.

* Then also comment what you tried, that way I'll know that you checked it. 🤓

## Create a Pull Request

///

This is of course not the frontend for the final users, but it's a great automatic tool to document interactively all your API.

It can be used by the frontend team (that can also be yourself).

It can be used by third party applications and systems.

And it can also be used by yourself, to debug, check and test the same application.

## The `password` flow

	// cmd represents the upgradeCheck command
	cmd := &cobra.Command{
		Use:   "precheck",
		Short: "Check whether Istio can safely be installed or upgraded",
		Long:  `precheck inspects a Kubernetes cluster for Istio install and upgrade requirements.`,
		Example: `  # Verify that Istio can be installed or upgraded
  istioctl x precheck

  # Check only a single namespace
  istioctl x precheck --namespace 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:

#### Install `openapi-ts`

You can install `openapi-ts` in your frontend code with:

<div class="termy">

```console
$ npm install @hey-api/openapi-ts --save-dev

---> 100%
```

</div>

#### Generate Client Code

To generate the client code you can use the command line application `openapi-ts` that would now be installed.

### Include the custom docs

Now you can create the *path operations* for the custom docs.

You can reuse FastAPI's internal functions to create the HTML pages for the docs, and pass them the needed arguments:

* `openapi_url`: the URL where the HTML page for the docs can get the OpenAPI schema for your API. You can use here the attribute `app.openapi_url`.
* `title`: the title of your API.

{!../../docs_src/bigger_applications/app/routers/users.py!}
```

You can think of `APIRouter` as a "mini `FastAPI`" class.

All the same options are supported.

All the same `parameters`, `responses`, `dependencies`, `tags`, etc.

/// tip

In this example, the variable is called `router`, but you can name it however you want.

///

     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_OS2 = "os/2";

    /**
     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_NETWARE = "netware";

    /**
     * OS family that can be tested for. {@value}
     */
    private static final String FAMILY_DOS = "dos";

    /**
     * OS family that can be tested for. {@value}
     */

# Path Parameters and Numeric Validations

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import Path

First, import `Path` from `fastapi`, and import `Annotated`:

//// tab | Python 3.10+

```Python hl_lines="1  3"
{!> ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py!}
```