This is particularly useful when automatically generating clients or
                SDKs for your API.

                Read more about it in the
                [FastAPI docs about how to Generate Clients](https://fastapi.tiangolo.com/advanced/generate-clients/#custom-generate-unique-id-function).
                """
            ),
        ] = Default(generate_unique_id),

                Read more about it in the
                [FastAPI docs about how to Generate Clients](https://fastapi.tiangolo.com/advanced/generate-clients/#custom-generate-unique-id-function).
                """
            ),
        ] = Default(generate_unique_id),
    ) -> None:
        """
        Include an `APIRouter` in the same app.

        Read more about it in the

            Read more about it in the
            [FastAPI docs about Query parameters](https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#declare-more-metadata)
            """
        ),
    ] = None,
    description: Annotated[
        str | None,
        Doc(
            """
            Human-readable description.

            Read more about it in the

blank_issues_enabled: false
contact_links:
  - name: Security Contact
    about: Please report security vulnerabilities to ******@****.***
  - name: Question or Problem
    about: Ask a question or ask about a problem in GitHub Discussions.
    url: https://github.com/fastapi/fastapi/discussions/categories/questions
  - name: Feature Request

## About Starlette { #about-starlette }

You shouldn't pin the version of `starlette`.

Different versions of **FastAPI** will use a specific newer version of Starlette.

So, you can just let **FastAPI** use the correct Starlette version.

## About Pydantic { #about-pydantic }

    * Read other ideas, articles, and read about tools I have created.
    * Follow me to read when I publish something new.

## Tweet about **FastAPI** { #tweet-about-fastapi }

[Tweet about **FastAPI**](https://x.com/compose/tweet?text=I'm loving @fastapi because... https://github.com/fastapi/fastapi) and let me and others know why you like it. 🎉

# About { #about }

            Configuration parameters for Swagger UI.

            It defaults to [swagger_ui_default_parameters][fastapi.openapi.docs.swagger_ui_default_parameters].

            Read more about it in the
            [FastAPI docs about how to Configure Swagger UI](https://fastapi.tiangolo.com/how-to/configure-swagger-ui/).
            """
        ),
    ] = None,
) -> HTMLResponse:
    """

                The OAuth2 spec says it is required and MUST be the fixed string
                "password". This dependency is strict about it. If you want to be
                permissive, use instead the `OAuth2PasswordRequestForm` dependency
                class.

                Read more about it in the
                [FastAPI docs for Simple OAuth2 with Password and Bearer](https://fastapi.tiangolo.com/tutorial/security/simple-oauth2/).

I think `Union[SomeType, None]` is more explicit about what it means.

It's just about the words and names. But those words can affect how you and your teammates think about the code.

As an example, let's take this function:

```python
from typing import Optional


def say_hi(name: Optional[str]):