`sig
type ('a, 'b) t
val empty : ('a, 'b) Tbl.t
val add : 'a -> 'b -> ('a, 'b) Tbl.t -> ('a, 'b) Tbl.t
val find : 'a -> ('a, 'b) Tbl.t -> 'b
val mem : 'a -> ('a, 'b) Tbl.t -> bool
val remove : 'a -> ('a, 'b) Tbl.t -> ('a, 'b) Tbl.t
val iter : ('a -> 'b -> unit) -> ('a, 'b) Tbl.t -> unit
val map : ('a -> 'b -> 'c) -> ('a, 'b) Tbl.t -> ('a, 'c) Tbl.t
val fold : ('a -> 'b -> 'c -> 'c) -> ('a, 'b) Tbl.t -> 'c -> 'c
val print :
(Format.formatter -> 'a -> unit) ->
(Format.formatter -> 'b -> unit) ->
Format.formatter -> ('a, 'b) Tbl.t -> unit
end`