I'm trying to increase the font of the header. I use the data-header-style property to do this My table html;

  <table data-row-style="rowStyle" data-header-style="headerStyle" class="table-responsive " id="tblPickupList">
                    <thead>
                        <tr>
                            <th data-field="CountryCode" data-visible="true">Ülke Kodu</th>
                            <th data-field="Country">Varış Ülkesi</th>
                            <th data-field="PickUpDate" data-formatter="DateFormatter">Pickup Tarihi</th>
                            <th data-field="ManifestDate" data-formatter="DateFormatter">Manifesto Tarihi</th>
                            <th data-field="MAWB">MAWB</th>
                            <th data-field="TotalBAGCount" data-sortable="true">Toplam Bag Sayısı</th>
                            <th data-field="TotalBAGWeight" style="text-align:right">Toplam Bag Ağırlığı</th>
                            <th data-field="TotalBAGWeightPhysical" style="text-align:right">Toplam Bag Fiziksel Ağırlığı</th>
                            <th data-field="">İşlemler</th>

                        </tr>
                    </thead>
                </table>

My js;

function headerStyle(column) {
console.log(column);
return {
    css: { 'font-size': '20px' },
    classes: 'bg-success'
}}



function rowStyle(row, index) {

var dateString = DateFormatter(row.PickUpDate);
var fullDate = dateString.split(".");
var day = Math.floor(fullDate[0]);
var month = Math.floor(fullDate[1]);
var year = Math.floor(fullDate[2]);

var today = new Date();
var todayDay = today.getDate();
var todayMonth = today.getMonth() + 1;
var todayYear = today.getFullYear();



if (todayDay == day && todayMonth == month && todayYear == year) {
    return {
        css: {
            'background-color': '#22bb33',
            color: 'black',
            'font-weight': 'bold',
            'font-size': '20px'
        }
    }
}
return {
    classes: 'bg-grey'
}}

The data-row-style property works. But the data-header-style does not.Even console.log in headerStyle function doesn't work.