}

    open fun receivedResponseAtMillis(receivedResponseAtMillis: Long) =
      apply {
        this.receivedResponseAtMillis = receivedResponseAtMillis
      }

    internal fun initExchange(exchange: Exchange) {
      this.exchange = exchange
      this.trailersFn = { exchange.trailers() }
    }

    open fun build(): Response {
      check(code >= 0) { "code < 0: $code" }