How to apply alternate row background for UnBoundRows in SfDataGrid?

<Window.Resources>
    <local:UnBoundRowStyleConverter x:Key="UnBoundRowStyleConverter" />
        <Style TargetType="Syncfusion:GridUnBoundRowCell">
            <Setter Property="Background" Value="{Binding Converter={StaticResource UnBoundRowStyleConverter}, RelativeSource={RelativeSource Self}}" />
        </Style>
</Window.Resources>

public class UnBoundRowStyleConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var index = (value as GridUnBoundRowCell).ColumnBase.RowIndex;
        if (index % 2 == 0)
            return Colors.Bisque.ToString();
        else
            return Colors.LightSkyBlue.ToString();
    }
 
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return null;
    }
}