How to use the mobx-keystone.ActionTrackingResult.Return function in mobx-keystone

onStart(actionCall, ctx) {
      if (!serverAction) {
        // if the action does not come from the server cancel it silently
        // and send it to the server
        // it will then be replicated by the server and properly executed
        server.sendMessage(serializeActionCall(actionCall, rootStore))

        ctx.data[cancelledActionSymbol] = true // just for logging purposes

        // "cancel" the action by returning undefined
        return {
          result: ActionTrackingResult.Return,
          value: undefined,
        }
      } else {
        // just run the server action unmodified
        return undefined
      }
    },
  })