    sig
      type extern_flags = No_sharing | Closures
      val to_channel :
        Pervasives.out_channel -> 'a -> Marshal.extern_flags list -> unit
      external to_string : 'a -> Marshal.extern_flags list -> string
        = "output_value_to_string"
      val to_buffer :
        string -> int -> int -> 'a -> Marshal.extern_flags list -> int
      val from_channel : Pervasives.in_channel -> 'a
      val from_string : string -> int -> 'a
      val header_size : int
      val data_size : string -> int -> int
      val total_size : string -> int -> int
    end