if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()
          responseBuilder = exchange.readResponseHeaders(expectContinue = true)
          exchange.responseHeadersStart()
          invokeStartEvent = false
        }
        if (responseBuilder == null) {
          if (requestBody.isDuplex()) {

   *
   * @param expectContinue true to return null if this is an intermediate response with a "100"
   * response code. Otherwise this method never returns null.
   */
  @Throws(IOException::class)
  fun readResponseHeaders(expectContinue: Boolean): Response.Builder?

  @Throws(IOException::class)
  fun reportedContentLength(response: Response): Long

  @Throws(IOException::class)

  }

  override fun flushRequest() {
    http2Connection.flush()
  }

  override fun finishRequest() {
    stream!!.sink.close()
  }

  override fun readResponseHeaders(expectContinue: Boolean): Response.Builder? {
    val stream = stream ?: throw IOException("stream wasn't created")
    val headers = stream.takeHeaders(callerIsIdle = expectContinue)