.add("\tkey\t:\tvalue\t") // '\t' also counts as whitespace
        .add("ping:  pong  ") // Value whitespace is trimmed.
        .add("kit:kat") // Space after colon is not required.
        .build()
    assertThat(headers.values("foo")).containsExactly("bar", "baz", "bak")
    assertThat(headers.values("key")).containsExactly("value")
    assertThat(headers.values("ping")).containsExactly("pong")

  internal const val OPCODE_CONTINUATION = 0x0
  internal const val OPCODE_TEXT = 0x1
  internal const val OPCODE_BINARY = 0x2

  internal const val OPCODE_CONTROL_CLOSE = 0x8
  internal const val OPCODE_CONTROL_PING = 0x9
  internal const val OPCODE_CONTROL_PONG = 0xa

  /**
   * Maximum length of frame payload. Larger payloads, if supported by the frame type, can use the
   * special values [PAYLOAD_SHORT] or [PAYLOAD_LONG].
   */

  const val TYPE_RST_STREAM = 0x3
  const val TYPE_SETTINGS = 0x4
  const val TYPE_PUSH_PROMISE = 0x5
  const val TYPE_PING = 0x6
  const val TYPE_GOAWAY = 0x7
  const val TYPE_WINDOW_UPDATE = 0x8
  const val TYPE_CONTINUATION = 0x9

  const val FLAG_NONE = 0x0
  const val FLAG_ACK = 0x1 // Used for settings and ping.
  const val FLAG_END_STREAM = 0x1 // Used for headers and data.

  }

  fun assertBinaryMessage(payload: ByteString?) {
    assertThat(nextEvent()).isEqualTo(Message(payload))
  }

  fun assertPing(payload: ByteString) {
    assertThat(nextEvent()).isEqualTo(Ping(payload))
  }

  fun assertPong(payload: ByteString) {
    assertThat(nextEvent()).isEqualTo(Pong(payload))
  }

  fun assertClosing(
    code: Int,
    reason: String,
  ) {

      this.type = Http2.TYPE_RST_STREAM
      this.streamId = streamId
      this.errorCode = errorCode
    }

    override fun ping(
      ack: Boolean,
      payload1: Int,
      payload2: Int,
    ) {
      check(type == -1)
      type = Http2.TYPE_PING
      this.ack = ack
      this.payload1 = payload1
      this.payload2 = payload2
    }

    override fun goAway(

  private val maskCursor: Buffer.UnsafeCursor? = if (isClient) Buffer.UnsafeCursor() else null

  /** Send a ping with the supplied [payload]. */
  @Throws(IOException::class)
  fun writePing(payload: ByteString) {
    writeControlFrame(OPCODE_CONTROL_PING, payload)
  }

  /** Send a pong with the supplied [payload]. */
  @Throws(IOException::class)
  fun writePong(payload: ByteString) {

  }

  @Test
  fun flagOverlapOn0x1() {
    assertThat(frameLog(true, 0, 0, TYPE_SETTINGS, 0x1))
      .isEqualTo("<< 0x00000000     0 SETTINGS      ACK")
    assertThat(frameLog(true, 0, 8, TYPE_PING, 0x1))
      .isEqualTo("<< 0x00000000     8 PING          ACK")
    assertThat(frameLog(true, 3, 0, TYPE_HEADERS, 0x1))
      .isEqualTo("<< 0x00000003     0 HEADERS       END_STREAM")
    assertThat(frameLog(true, 3, 0, TYPE_DATA, 0x1))

# sudo apt-get update && apt-get whichever

# hadolint ignore=DL3005,DL3008
RUN apt-get update && \
  apt-get install --no-install-recommends -y \
  ca-certificates \
  curl \
  iptables \
  iproute2 \
  iputils-ping \
  knot-dnsutils \
  netcat-openbsd \
  tcpdump \
  conntrack \
  bsdmainutils \
  net-tools \
  lsof \
  sudo \
  && update-ca-certificates \
  && apt-get upgrade -y \
  && apt-get clean \

    fail("")
  }

  override fun settings(
    clearPrevious: Boolean,
    settings: Settings,
  ) {
    fail("")
  }

  override fun ackSettings() {
    fail("")
  }

  override fun ping(
    ack: Boolean,
    payload1: Int,
    payload2: Int,
  ) {
    fail("")
  }

  override fun goAway(
    lastGoodStreamId: Int,
    errorCode: ErrorCode,
    debugData: ByteString,
  ) {

The benefit of raising an exception over `return`ing a value will be more evident in the section about Dependencies and Security.

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

```Python hl_lines="11"