# Module type MoreLabels.Map.S

    module type S = sig .. end

    type key

    type +'a t

    val empty : 'a t

    val is_empty : 'a t -> bool

    val mem : key -> 'a t -> bool

    val add : key:key ->
           data:'a -> 'a t -> 'a t

    val singleton : key -> 'a -> 'a t

    val remove : key -> 'a t -> 'a t

    val merge : f:(key -> 'a option -> 'b option -> 'c option) ->
           'a t -> 'b t -> 'c t

    val union : f:(key -> 'a -> 'a -> 'a option) ->
           'a t -> 'a t -> 'a t

    val compare : cmp:('a -> 'a -> int) ->
           'a t -> 'a t -> int

    val equal : cmp:('a -> 'a -> bool) ->
           'a t -> 'a t -> bool

    val iter : f:(key:key -> data:'a -> unit) ->
           'a t -> unit

    val fold : f:(key:key -> data:'a -> 'b -> 'b) ->
           'a t -> init:'b -> 'b

    val for_all : f:(key -> 'a -> bool) -> 'a t -> bool

    val exists : f:(key -> 'a -> bool) -> 'a t -> bool

    val filter : f:(key -> 'a -> bool) ->
           'a t -> 'a t

    val partition : f:(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 : f:('a -> 'b) -> 'a t -> 'b t

    val mapi : f:(key -> 'a -> 'b) ->
           'a t -> 'b t