`inherit optGroupElement`
`method form : formElement Js_of_ocaml__.Js.t Js_of_ocaml__.Js.opt Js_of_ocaml__.Js.readonly_prop`
`method defaultSelected : bool Js_of_ocaml__.Js.t Js_of_ocaml__.Js.prop`
`method text : Js_of_ocaml__.Js.js_string Js_of_ocaml__.Js.t Js_of_ocaml__.Js.readonly_prop`
`method index : int Js_of_ocaml__.Js.readonly_prop`
`method selected : bool Js_of_ocaml__.Js.t Js_of_ocaml__.Js.prop`
`method value : Js_of_ocaml__.Js.js_string Js_of_ocaml__.Js.t Js_of_ocaml__.Js.prop`