rcopytype with multiple S3 classes

[marcpabst]

Often, an R list will have multiple class attributes: - attr(*, "class")= chr [1:3] "class1" "class2" "class3". For a single class, rcopytype(::Type{RClass{:class}}, s::Ptr{VecSxp}) = MyTypeseems to work, but is there any way to register a custom conversion using rcopytype() for lists that have multiple class attributes?