if (associatedStreamId == 0) {
        writer.headers(outFinished, streamId, requestHeaders)
      } else {
        require(!client) { "client streams shouldn't have associated stream IDs" }
        // HTTP/2 has a PUSH_PROMISE frame.
        writer.pushPromise(associatedStreamId, streamId, requestHeaders)
      }
    }

    if (flushHeaders) {
      writer.flush()
    }

    return stream
  }