Registration of S3 class "zoo"
as a formally defined class. Used here
to allow the "zoo"
class to appear in method signatures.
A virtual Class: No objects may be created from it.
showClass("zoo")
#> Virtual Class "zoo" [package "wql"]
#>
#> Slots:
#>
#> Name: .S3Class
#> Class: character
#>
#> Extends: "oldClass"