Arg.Set
type arg = t
val is_empty : t -> bool
val empty : t
val add : arg -> completion -> t -> t
val choose : t -> arg * completion
val partition : (arg -> completion -> bool) -> t -> t * t
val filter : (arg -> completion -> bool) -> t -> t
val iter : (arg -> completion -> unit) -> t -> unit
val singleton : arg -> completion -> t
val fold : (arg -> completion -> 'acc -> 'acc) -> t -> 'acc -> 'acc
val find_opt : arg -> t -> completion option