from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: str | None = Header(default=None, convert_underscores=False),
):

from typing import Union

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: Union[str, None] = Header(default=None, convert_underscores=False),
):

):
    return {"hidden_cookie": hidden_cookie}


@app.get("/hidden_header")
async def hidden_header(
    hidden_header: Optional[str] = Header(default=None, include_in_schema=False),
):
    return {"hidden_header": hidden_header}


@app.get("/hidden_path/{hidden_path}")
async def hidden_path(hidden_path: str = Path(include_in_schema=False)):

                "value": "query2",
            },
        },
    ),
):
    return data


@app.get("/header_examples/")
def header_examples(
    data: Union[str, None] = Header(
        default=None,
        examples=[
            "json_schema_header1",
            "json_schema_header2",
        ],
        openapi_examples={
            "Header One": {

        ),
        deprecated(
            """
            The `extra` kwargs is deprecated. Use `json_schema_extra` instead.
            """
        ),
    ],
) -> Any:
    return params.Header(
        default=default,
        default_factory=default_factory,
        alias=alias,
        alias_priority=alias_priority,
        validation_alias=validation_alias,
        serialization_alias=serialization_alias,

			case TypeGNULongName:
				gnuLongName = p.parseString(realname)
			case TypeGNULongLink:
				gnuLongLink = p.parseString(realname)
			}
			continue // This is a meta header affecting the next header
		default:
			// The old GNU sparse format is handled here since it is technically
			// just a regular file with additional attributes.

			if err := mergePAX(hdr, paxHdrs); err != nil {
				return nil, err
			}

	public final fun handshake ()Lokhttp3/Handshake;
	public final fun header (Ljava/lang/String;)Ljava/lang/String;
	public final fun header (Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
	public static synthetic fun header$default (Lokhttp3/Response;Ljava/lang/String;Ljava/lang/String;ILjava/lang/Object;)Ljava/lang/String;
	public final fun headers ()Lokhttp3/Headers;
	public final fun headers (Ljava/lang/String;)Ljava/util/List;

@app.get("/items/{item_id}")
def main(
    item_id: int = Path(default=..., gt=0),
    query: str = Query(default=..., max_length=10),
    session: str = Cookie(default=..., min_length=3),
    x_trace: str = Header(default=..., title="Tracing header"),
):
    return {"message": "Hello World"}
```

...all these parameters are required because the default value is `...` (Ellipsis).