How to use the rx-jupyter.sessions.update function in rx-jupyter

mergeMap(({ response }) => {
          const { id: kernelId } = response;
          const sessionPayload = {
            kernel: { id: kernelId, name: kernelSpecName }
          };
          // The sessions API will close down the old kernel for us if it is
          // on this session
          return sessions.update(serverConfig, sessionId, sessionPayload).pipe(
            mergeMap(({ response: session }) => {
              const kernel: RemoteKernelProps = Object.assign(
                {},
                session.kernel,
                {
                  type: "websocket",
                  sessionId,
                  cwd,
                  channels: kernels.connect(
                    serverConfig,
                    session.kernel.id,
                    sessionId
                  ),
                  kernelSpecName
                }
              );

mergeMap(({ response }) => {
          const { id: kernelId } = response;
          const sessionPayload = {
            kernel: { id: kernelId, name: kernelSpecName }
          };
          // The sessions API will close down the old kernel for us if it is
          // on this session
          return sessions.update(serverConfig, sessionId, sessionPayload).pipe(
            mergeMap(({ response: session }) => {
              const kernel: RemoteKernelProps = Object.assign(
                {},
                session.kernel,
                {
                  type: "websocket",
                  sessionId,
                  cwd,
                  channels: kernels.connect(
                    serverConfig,
                    session.kernel.id,
                    sessionId
                  ),
                  kernelSpecName
                }
              );