/** The exception that explains [errorCode]. Null if no exception was provided. */
  internal var errorException: IOException? = null

  init {
    if (headers != null) {
      check(!isLocallyInitiated) { "locally-initiated streams shouldn't have headers yet" }
      headersQueue += headers
    } else {
      check(isLocallyInitiated) { "remotely-initiated streams should have headers" }
    }
  }

  /**