R does not know `registerShinyDebugHook`, so it will warn against it in `R CMD check`, although the code here is totally legitimate here (it is just a gory detail of `R CMD check`); one way to avoid the warning is

```
registerShinyDebugHook <- get("registerShinyDebugHook", mode = "function")
```

Then use it.

Or declare it outside as `globalVariables("registerShinyDebugHook")`.

You do not need to take care of this if you do not understand it. I can do it after the pull request is merged by someone (whom?)