Batteries user guide : BatOptParse.Opt

`sig
exception No_value
exception Option_error of string * string
exception Option_help
type 'a t = {
option_set : string -> string list -> unit;
option_set_value : 'a -> unit;
option_get : unit -> 'a option;
option_metavars : string list;
option_defhelp : string option;
}
val get : 'a BatOptParse.Opt.t -> 'a
val set : 'a BatOptParse.Opt.t -> 'a -> unit
val opt : 'a BatOptParse.Opt.t -> 'a option
val is_set : 'a BatOptParse.Opt.t -> bool
val value_option :
string ->
'a option ->
(string -> 'a) -> (exn -> string -> string) -> 'a BatOptParse.Opt.t
val callback_option :
string ->
(string -> 'a) ->
(exn -> string -> string) -> ('a -> unit) -> unit BatOptParse.Opt.t
end`