* `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as
   * a part of the response to `streamId`. The `promisedStreamId` has a priority of one greater than
   * `streamId`.
   *
   * @param streamId client-initiated stream ID.  Must be an odd number.
   * @param promisedStreamId server-initiated stream ID.  Must be an even number.

      routes = routes,
      attempt = 0,
      tunnelRequest = tunnelRequest,
      connectionSpecIndex = -1,
      isTlsFallback = false,
    )
  }

  /**
   * Returns a request that creates a TLS tunnel via an HTTP proxy. Everything in the tunnel request
   * is sent unencrypted to the proxy server, so tunnels include only the minimum set of headers.

  /**
   * A source that reads the incoming data frames of a stream. Although this class uses
   * synchronization to safely receive incoming data frames, it is not intended for use by multiple
   * readers.
   */
  inner class FramingSource internal constructor(
    /** Maximum number of bytes to buffer before reporting a flow control error. */
    private val maxByteCount: Long,
    /**