libvariantslib-ocaml-dev 1:0.13.0-1 (amd64 binary) in ubuntu focal

 Variantslib generates code to support variants as first class by
 adding "with variants" suffix to variants definition, e.g.,
 .
 type t =
 | First
 | Second
 | Third
 .
 with variants
 .
 This package contains development files.