```
setClass("Root")
setClass("Base", contains = "Root", representation(length = "integer"))
setClass("A", contains = "Base", representation(x = "numeric"))
setClass("B", contains = "Base", representation(y = "character"))
setClass("C", contains = c("A", "B"))
extends("C") #--> "C" "A" "B" "Base" "Root"
selectSuperClasses("C") # "A" "B"
selectSuperClasses("C", direct=FALSE) # "A" "B" "Base" "Root"
selectSuperClasses("C", dropVirt = TRUE, direct=FALSE)# ditto w/o "Root"
```

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