/** Removes all headers named [name] on this builder. */
    open fun removeHeader(name: String) = commonRemoveHeader(name)

    /** Removes all headers on this builder and adds [headers]. */
    open fun headers(headers: Headers) = commonHeaders(headers)

    /**
     * Sets this request's `Cache-Control` header, replacing any cache control headers already

```

////

/// warning

Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

///

## Duplicate headers

It is possible to receive duplicate headers. That means, the same header with multiple values.

You can define those cases using a list in the type declaration.

    assert response.json() == {"detail": "Not authenticated"}
    assert response.headers["WWW-Authenticate"] == "Bearer"


@needs_py310
def test_token(client: TestClient):
    access_token = get_access_token(scope="me", client=client)
    response = client.get(
        "/users/me", headers={"Authorization": f"Bearer {access_token}"}
    )
    assert response.status_code == 200, response.text

    assert response.json() == {"detail": "Not authenticated"}
    assert response.headers["WWW-Authenticate"] == "Bearer"


@needs_py39
def test_token(client: TestClient):
    access_token = get_access_token(scope="me", client=client)
    response = client.get(
        "/users/me", headers={"Authorization": f"Bearer {access_token}"}
    )
    assert response.status_code == 200, response.text

    val body = "hello".toRequestBody()
    val headers = headersOf("User-Agent", "RequestTest")
    val method = "PUT"
    val request =
      Request(
        url = url,
        headers = headers,
        method = method,
        body = body,
      )
    assertThat(request.url).isEqualTo(url)
    assertThat(request.headers).isEqualTo(headers)
    assertThat(request.method).isEqualTo(method)

	public fun <init> ()V
	public fun <init> (I)V
	public fun <init> (ILokhttp3/Headers;)V
	public fun <init> (ILokhttp3/Headers;Ljava/lang/String;)V
	public fun <init> (ILokhttp3/Headers;Ljava/lang/String;Z)V
	public fun <init> (ILokhttp3/Headers;Ljava/lang/String;ZLmockwebserver3/SocketPolicy;)V
	public synthetic fun <init> (ILokhttp3/Headers;Ljava/lang/String;ZLmockwebserver3/SocketPolicy;ILkotlin/jvm/internal/DefaultConstructorMarker;)V

    response = client.get("/users/me", headers={"Authorization": "Bearer nonexistent"})
    assert response.status_code == 401, response.text
    assert response.json() == {"detail": "Invalid authentication credentials"}
    assert response.headers["WWW-Authenticate"] == "Bearer"


@needs_py310
def test_incorrect_token_type(client: TestClient):
    response = client.get(
        "/users/me", headers={"Authorization": "Notexistent testtoken"}

    response = client.get("/users/me", headers={"Authorization": "Bearer nonexistent"})
    assert response.status_code == 401, response.text
    assert response.json() == {"detail": "Invalid authentication credentials"}
    assert response.headers["WWW-Authenticate"] == "Bearer"


@needs_py310
def test_incorrect_token_type(client: TestClient):
    response = client.get(
        "/users/me", headers={"Authorization": "Notexistent testtoken"}

```

////

**FastAPI** will **extract** the data for **each field** from the **headers** in the request and give you the Pydantic model you defined.

## Check the Docs

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers

      result.add(Header(TARGET_SCHEME, request.url.scheme))

      for (i in 0 until headers.size) {
        // header names must be lowercase.
        val name = headers.name(i).lowercase(Locale.US)
        if (name !in HTTP_2_SKIPPED_REQUEST_HEADERS ||
          name == TE && headers.value(i) == "trailers"
        ) {
          result.add(Header(name, headers.value(i)))
        }
      }
      return result
    }