How to validate inside `handleRecordCreation()` or `mutateFormDataBeforeSave`

Hello guys, hope you're doing well!
I want to validate or use a custom validation rule inside

mutateFormDataBeforeSave()

mutateFormDataBeforeSave()

mutateFormDataBeforeSave()

mutateFormDataBeforeSave(), wonder how to do that?

Thanks in advance!

Solution

$get('../../id')

$get('../../id')

$get('../../id')

$get('../../id')
?