`functor (Ord : OrderedType) -> sig type key = Ord.t type +'a t val empty : 'a t val is_empty : 'a t -> bool val mem : key -> 'a t -> bool val add : key -> 'a -> 'a t -> 'a t val singleton : key -> 'a -> 'a t val remove : key -> 'a t -> 'a t val merge : (key -> 'a option -> 'b option -> 'c option) -> 'a t -> 'b t -> 'c t val union : (key -> 'a -> 'a -> 'a option) -> 'a t -> 'a t -> 'a t val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool val iter : (key -> 'a -> unit) -> 'a t -> unit val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b val for_all : (key -> 'a -> bool) -> 'a t -> bool val exists : (key -> 'a -> bool) -> 'a t -> bool val filter : (key -> 'a -> bool) -> 'a t -> 'a t val partition : (key -> 'a -> bool) -> 'a t -> 'a t * 'a t val cardinal : 'a t -> int val bindings : 'a t -> (key * 'a) list val min_binding : 'a t -> key * 'a val max_binding : 'a t -> key * 'a val choose : 'a t -> key * 'a val split : key -> 'a t -> 'a t * 'a option * 'a t val find : key -> 'a t -> 'a val map : ('a -> 'b) -> 'a t -> 'b t val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t end`