`sig
type 'a conv = Parsetree.expression -> ('a, string) Result.result
val expr : Parsetree.expression Ppx_deriving.Arg.conv
val bool : bool Ppx_deriving.Arg.conv
val int : int Ppx_deriving.Arg.conv
val string : string Ppx_deriving.Arg.conv
val char : char Ppx_deriving.Arg.conv
val enum : string list -> string Ppx_deriving.Arg.conv
val list : 'a Ppx_deriving.Arg.conv -> 'a list Ppx_deriving.Arg.conv
val get_attr :
deriver:string ->
'a Ppx_deriving.Arg.conv -> Parsetree.attribute option -> 'a option
val get_flag : deriver:string -> Parsetree.attribute option -> bool
val get_expr :
deriver:string -> 'a Ppx_deriving.Arg.conv -> Parsetree.expression -> 'a
end`