{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

O **FastAPI** irá **extrair** os dados de **cada campo** a partir dos **cabeçalhos** da requisição e te retornará o modelo do Pydantic que você definiu.

### Checando a documentação

Você pode ver os headers necessários na interface gráfica da documentação em `/docs`:

    internal val reader: Http2Reader,
  ) : Http2Reader.Handler,
    () -> Unit {
    override fun invoke() {
      var connectionErrorCode = ErrorCode.INTERNAL_ERROR
      var streamErrorCode = ErrorCode.INTERNAL_ERROR
      var errorException: IOException? = null
      try {
        reader.readConnectionPreface(this)
        while (reader.nextFrame(false, this)) {
        }

Koki Igarashi <******@****.***> 1581071331 +0900

      length: Int,
    )

    /**
     * Create or update incoming headers, creating the corresponding streams if necessary. Frames
     * that trigger this are HEADERS and PUSH_PROMISE.
     *
     * @param inFinished true if the sender will not send further frames.
     * @param streamId the stream owning these headers.
     * @param associatedStreamId the stream that triggered the sender to create this stream.
     */

    }
  }

  private fun headersToList(response: MockResponse): List<String> {
    val headers = response.headers
    val size = headers.size
    val headerList: MutableList<String> = ArrayList(size)
    for (i in 0 until size) {
      headerList.add(headers.name(i) + ": " + headers.value(i))
    }
    return headerList
  }

  @Test
  fun shutdownWithoutStart() {

   * including any potential composed values.
   *
   * If there's nothing to read and no default value, this will throw an exception.
   */
  fun fromDer(reader: DerReader): T

  fun fromDer(byteString: ByteString): T {
    val buffer = Buffer().write(byteString)
    val reader = DerReader(buffer)
    return fromDer(reader)
  }

  /**

      assertThat(ioe.message).isEqualTo("Premature EOF")
    }
  }

  private fun headersToList(response: MockResponse.Builder): List<String> {
    val headers = response.build().headers
    return headers.map { (key, value) -> "$key: $value" }.toList()
  }

  @Test
  fun closeWithoutStart() {
    val server = MockWebServer()
    server.close()
  }

  @Test

render.svg...

	for {
		header, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			t.Fatalf("Failed to read header: %s", err)
		}
		if header.Typeflag != TypeReg {
			t.Fatalf("Typeflag should've been %d, found %d", TypeReg, header.Typeflag)
		}
	}
}

// failOnceWriter fails exactly once and then always reports success.
type failOnceWriter bool

    }

    /**
     * Checks if `expected` and `observed` are equal when viewed as a set and headers are
     * deduped.
     *
     * TODO: See if duped headers should be preserved on decode and verify.
     */
    private fun assertSetEquals(
      message: String,
      expected: List<Header>,
      observed: List<Header>,
    ) {
      assertThat(LinkedHashSet(observed), message)
        .isEqualTo(LinkedHashSet(expected))