jqGrid add multi select column filter to a specific column

I am trying to add the multi-select filter to my "PROVIDER" column in the jqGrid. I am able to add the select filter but now I am converting it to the multi-select filter. I referred to a few old posts here and tried to do the same. It's not throwing me any error but it is not creating the multi-select filter also. Please let me know what I am doing wrong below. I am able to get the unique values and able to create the SELECT list, I am guessing something is wrong with function dataInitMultiselect because I tried to console.log(elem) but it's not returning anything, not even undefined but the function is getting called because its not throwing me undefined function error.

Please, Please help me with this. I am struck on this more than 1 day now.

$("#home_grid").jqGrid({
        url: "/URL_TO_FETCH_DATA",
        datatype: "json",
        mtype: "GET",
        colNames: ["Provider", "Title","Original Publish Time", "Fetch Time"],
        colModel:
        [
            {
                name    : "PROVIDER",
                align   : "center",
                width   : "120%",
                search  : true
            },
            {
                name    : "TITLE",
                align   : "center",
                search  : true,
                width   : "250%",
                formatter: Title_Url_Bind 
            },
            {
                name        : "PUBLISH_TIME",
                align       : "center",
                width       : "130%",
                search      : true,
                sorttype    : "datetime"

            },
            {
                name        : "DB_ENTRY_TIME",
                align       : "center",
                width       : "130%",
                sortable    : true,
                sorttype    : "datetime"
            }
        ],
        pager       : "#home_pager",
        loadonce    : true,
        shrinkToFit : true,
        rowNum      : 10,
        autoHeight  : true,
        rowList     : [10, 15, 20, 25, 50],
        sortable    : true,
        viewrecords : true,
        toolbar     : [true, "top"],
        autowidth   : true,
        beforeProcessing: beforeProcessingHandler1,
    });

    function beforeProcessingHandler1(data) {
        initializeGridFilterValueDem(data);
    }

    initializeGridFilterValueDem = function (data) {
        setSearchSelect("Provider", jQuery("#home_grid"), data);
    }

    setSearchSelect = function (columnName, grid,data) {
        grid.jqGrid('setColProp', columnName,
            {
                searchoptions: {
                    clearSearch: false,
                    sopt: ['eq', 'ne'],
                    value: buildSearchSelect(getUniqueNames(columnName, data,grid)),
                    attr: { multiple: 'multiple', size: 7},
                    dataInit: dataInitMultiselect
                }
            }
        );
    }

    buildSearchSelect = function (uniqueNames) {
        var values = "";
        $.each(uniqueNames, function () {
            values += this + ":" + this + ";";
        });
        return values.substring(0, values.length - 1);
    }

    getUniqueNames = function (columnName, mydata_parm, grid) {

        var mydata = grid.jqGrid("getGridParam", "data");

        var texts = $.map(mydata, function (item) {
            return item[columnName];
        }),

        uniqueTexts = [], textsLength = texts.length, text, textsMap = {}, i;

        for (i = 0; i < textsLength; i++) {
            text = texts[i];
            if (text !== undefined && textsMap[text] === undefined) {
                // to test whether the texts is unique we place it in the map.
                textsMap[text] = true;
                uniqueTexts.push(text);
            }
        }

        return uniqueTexts;
    }

    dataInitMultiselect = function (elem) {
        console.log(elem);
        setTimeout(function () {
            var $elem = $(elem), id = elem.id,
                inToolbar = typeof id === "string" && id.substr(0, 3) === "gs_",
                options = {
                    selectedList: 2,
                    height: "auto",
                    checkAllText: "all",
                    uncheckAllText: "no",
                    noneSelectedText: "Any",
                    open: function () {
                        var $menu = $(".ui-multiselect-menu:visible");
                        $menu.width("auto");
                        return;
                    }
                },
                $options = $elem.find("option");
            if ($options.length > 0 && $options[0].selected) {
                $options[0].selected = false; // unselect the first selected option
            }
            if (inToolbar) {
                options.minWidth = 'auto';
            }
            //$elem.multiselect(options);
            $elem.multiselect(options).multiselectfilter({ placeholder: '' });
            $elem.siblings('button.ui-multiselect').css({
                width: inToolbar ? "98%" : "100%",
                marginTop: "1px",
                marginBottom: "1px",
                paddingTop: "3px"
            });
        }, 50);

    };

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