`object
method charset : string
method content_type :
unit -> string * (string * Netmime_string.s_param) list
method filename : string option
method finalize : unit -> unit
method name : string
method open_value_rd : unit -> Netchannels.in_obj_channel
method representation :
[ `MIME of Netmime.mime_message | `Simple of Netmime.mime_body ]
method store : [ `File of string | `Memory ]
method value : string
end`