With flatten = FALSE, a structured S3 object is returned.
The S3 object only has one slot, which is called levels.
This contains a named list. Each name refers to package from the call to
parallelRegisterLevels, while the entries are character
vectors of the form “package.level”.
With flatten = TRUE, a simple character vector is returned that contains all
concatenated entries of levels from above.
parallelGetRegisteredLevels(flatten = FALSE)[logical(1)]
Flatten to character vector or not? See description.
Default is FALSE.
[codeRegisteredLevels | character]. See above.