`sig
module Key :
sig
type ('a, 'b) t
val create :
init:'b ->
f:('b -> 'a -> 'b) ->
name:string ->
('b -> Std_internal.Sexp.t) -> ('a, 'b) Univ_map.With_fold.Key.t
end
val set : t -> ('a, 'b) Univ_map.With_fold.Key.t -> 'b -> t
val find : t -> ('a, 'b) Univ_map.With_fold.Key.t -> 'b
val add : t -> ('a, 'b) Univ_map.With_fold.Key.t -> 'a -> t
val change : t -> ('a, 'b) Univ_map.With_fold.Key.t -> ('b -> 'b) -> t
end`