`sig
val string : string Command.Arg_type.t
val int : int Command.Arg_type.t
val char : char Command.Arg_type.t
val float : float Command.Arg_type.t
val bool : bool Command.Arg_type.t
val date : Date.t Command.Arg_type.t
val time : Time.t Command.Arg_type.t
val time_ofday : Time.Ofday.Zoned.t Command.Arg_type.t
val time_ofday_unzoned : Time.Ofday.t Command.Arg_type.t
val time_span : Time.Span.t Command.Arg_type.t
val file : string Command.Arg_type.t
end`