* reads of the [ResponseBody]. For duplex request bodies, [writeTo] should return
   * quickly, possibly by handing off the provided request body to another thread to perform
   * writing.
   *
   * [grpc]: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
   */
  open fun isDuplex(): Boolean = commonIsDuplex()

  /**
   * Returns true if this body expects at most one call to [writeTo] and can be transmitted