bootstrap-select (selectpicker) make collapsible with optgroup

selectpicker-collapsible.js

// Selectpicker converts to collapsible when the inside has a optgroup
$('.selectpicker').on('shown.bs.select', function (e, clickedIndex, isSelected, previousValue) {
    if ($(e.target).find("optgroup").length > 0) {
        //.bootstrap-select .dropdown-menu .dropdown-header
        $(e.target).closest(".bootstrap-select").find(".dropdown-menu .dropdown-header").click(function (e) {
            e.stopImmediatePropagation();

            var $this = $(this),
                $thisOpt = $this.attr("class").split(" ")[1],
                $opt = $this.siblings("li").not(".dropdown-header, .dropdown-divider");

            $($opt).filter(function (i, item) {
                return $(item).hasClass($thisOpt);
            }).toggleClass("d-block");
        });


        // Hide option tags when init without first element
        var $this = $(e.target).closest(".bootstrap-select").find(".dropdown-menu .dropdown-header"),
            $opt = $this.siblings("li").not(".dropdown-header, .dropdown-divider");

        $($opt).filter(function (i, item) {
            return $(item).hasClass("optgroup-1");
        }).addClass("d-block");

    }
});