}
			type version struct {
				Idx      int
				Header   json.RawMessage
				Metadata json.RawMessage
			}
			versions := make([]version, nVers)
			e = decodeVersions(v, nVers, func(idx int, hdr, meta []byte) error {
				var header xlMetaV2VersionHeaderV2
				if _, e := header.UnmarshalMsg(hdr); e != nil {
					return e
				}
				b, e := header.MarshalJSON()
				if e != nil {
					return e
				}

        .header("User-Agent", "OkHttp Headers.java")
        .addHeader("Accept", "application/json; q=0.5")
        .addHeader("Accept", "application/vnd.github.v3+json")
        .build()

    client.newCall(request).execute().use { response ->
      if (!response.isSuccessful) throw IOException("Unexpected code $response")

      println("Server: ${response.header("Server")}")
      println("Date: ${response.header("Date")}")

Diese Proxys könnten HTTPS-Zertifikate und andere Dinge handhaben.

## Proxy-<abbr title="weitergeleitete Header">Forwarded-Header</abbr> { #proxy-forwarded-headers }

///

/// warning | Achtung

Sie können mehrere `File`- und `Form`-Parameter in einer *Pfadoperation* deklarieren, aber Sie können nicht gleichzeitig auch `Body`-Felder deklarieren, welche Sie als JSON erwarten, da der <abbr title="Request – Anfrage: Daten, die der Client zum Server sendet">Request</abbr> den Body mittels `multipart/form-data` statt `application/json` kodiert.

Das ist keine Limitation von **FastAPI**, sondern Teil des HTTP-Protokolls.

## Conceitos de Implantação { #deployment-concepts }

Aqui você viu como usar vários **trabalhadores** para **paralelizar** a execução do aplicativo, aproveitar **vários núcleos** na CPU e conseguir atender **mais solicitações**.

Da lista de conceitos de implantação acima, o uso de trabalhadores ajudaria principalmente com a parte da **replicação** e um pouco com as **reinicializações**, mas você ainda precisa cuidar dos outros:

from fastapi import Depends, FastAPI, Header, status
from fastapi.testclient import TestClient

app = FastAPI()


def get_header(*, someheader: str = Header()):
    return someheader


def get_something_else(*, someheader: str = Depends(get_header)):
    return f"{someheader}123"


@app.get("/")
def get_deps(dep1: str = Depends(get_header), dep2: str = Depends(get_something_else)):
    return {"dep1": dep1, "dep2": dep2}

	// Reference:
	//	http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_06
	FormatUSTAR

	// FormatPAX represents the PAX header format defined in POSIX.1-2001.
	//
	// PAX extends USTAR by writing a special file with Typeflag TypeXHeader
	// preceding the original header. This file contains a set of key-value
	// records, which are used to overcome USTAR's shortcomings, in addition to

* `headers` - Un `dict` de strings.
* `media_type` - Un `str` que da el media type. Por ejemplo, `"text/html"`.

FastAPI (de hecho Starlette) incluirá automáticamente un header Content-Length. También incluirá un header Content-Type, basado en el `media_type` y añadiendo un conjunto de caracteres para tipos de texto.

{* ../../docs_src/response_directly/tutorial002_py39.py hl[1,18] *}

    """
    Add or update header permalinks in specific pages of En docs.
    """
    for md_file in pages:
        add_permalinks_page(md_file, update_existing=update_existing)


@app.command()
def add_permalinks(update_existing: bool = False) -> None:
    """
    Add or update header permalinks in all pages of En docs.
    """

from typing import Union

from fastapi import FastAPI, Header

app = FastAPI()


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