How to customize the expander icon for each level of group in Xamarin.Forms DataGrid(SfDataGrid)?

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             x:Class="DataGridDemo.MainPage"
             xmlns:local="clr-namespace:DataGridDemo"
             xmlns:syncfusion="clr-namespace:Syncfusion.SfDataGrid.XForms;assembly=Syncfusion.SfDataGrid.XForms"
             Padding="10,10,10,10">
    <ContentPage.Resources>
        <ResourceDictionary>
            <local:GroupCaptionConverter x:Key="SummaryConverter" />
            <local:GroupBackgroundColor x:Key="SummaryBackground" />
            <local:GroupIconConverter x:Key="SummaryIcon"></local:GroupIconConverter>
        </ResourceDictionary>
    </ContentPage.Resources>
    <ContentPage.BindingContext>
        <local:OrderInfoRepository x:Name="viewModel"/>
    </ContentPage.BindingContext>
    <ContentPage.Content>
        <syncfusion:SfDataGrid
            x:Name="dataGrid"
             ItemsSource="{Binding OrderInfoCollection}"
             AutoGenerateColumns="False"
            AllowGroupExpandCollapse="True"
            ColumnSizer="Star"
             GroupingMode="Multiple"
             AllowEditing="True"
             NavigationMode="Cell"
             SelectionMode="Single">
            <syncfusion:SfDataGrid.GroupColumnDescriptions>
                <syncfusion:GroupColumnDescription ColumnName="OrderID" />
                <syncfusion:GroupColumnDescription ColumnName="CustomerID" />
            </syncfusion:SfDataGrid.GroupColumnDescriptions>
            <syncfusion:SfDataGrid.Columns>
                <syncfusion:GridTextColumn HeaderText="Order ID" MappingName="OrderID" />
                <syncfusion:GridTextColumn HeaderText="Customer ID" MappingName="CustomerID" />
                
                <syncfusion:GridTextColumn HeaderText="City" MappingName="ShipCity" />
                <syncfusion:GridTextColumn HeaderText="Ship Country" MappingName="ShipCountry" />
            </syncfusion:SfDataGrid.Columns>
            <syncfusion:SfDataGrid.CaptionSummaryTemplate>
                <DataTemplate>
                    <Grid Padding="5"  HorizontalOptions="CenterAndExpand" BackgroundColor="{Binding Converter={StaticResource SummaryBackground}, ConverterParameter={x:Reference dataGrid}}">
 
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"></ColumnDefinition>
                            <ColumnDefinition Width="*"></ColumnDefinition>
                        </Grid.ColumnDefinitions>
                        <Label Grid.Column="0" x:Name="captionSummary" VerticalOptions="CenterAndExpand" WidthRequest="250"  Text="{Binding Converter={StaticResource SummaryConverter}, 
                                                  ConverterParameter = {x:Reference dataGrid} }" >
                            
                        </Label>
                        <Image Grid.Column="1" Source="{Binding Converter={StaticResource SummaryIcon}, ConverterParameter={x:Reference dataGrid}}" VerticalOptions="Center" HorizontalOptions="End" HeightRequest="20">
                            
                        </Image>
                    </Grid>
                </DataTemplate>
            </syncfusion:SfDataGrid.CaptionSummaryTemplate>
 
 
        </syncfusion:SfDataGrid>
    </ContentPage.Content>
</ContentPage>
 

public class GroupCaptionConverter : IValueConverter
    {
        public string Name { get; set; }
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var data = value != null ? value as Group : null;
            if (data != null)
            {
                SfDataGrid dataGrid = (SfDataGrid)parameter;
                if ((value as Group).Parent is TopLevelGroup)
                {
                    return dataGrid.View.TopLevelGroup.GetGroupCaptionText( (value as Group), "{ColumnName} : {Key} - {ItemsCount} Items", dataGrid.GroupColumnDescriptions[0].ColumnName);
                }
                else
                {
                    return dataGrid.View.TopLevelGroup.GetGroupCaptionText((value as Group), "{ColumnName} : {Key} - {ItemsCount} Items", dataGrid.GroupColumnDescriptions[1].ColumnName);
                }
            }
            return null;
        }
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }
 
 
    public class GroupBackgroundColor : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var data = value != null ? value as Group : null;
            if (data != null)
            {
                SfDataGrid dataGrid = (SfDataGrid)parameter;
                if ((value as Group).Parent is TopLevelGroup)
                {
                    return "LightGray";
                }
                else
                {
                    return "LightBlue";
                }
            }
            return null;
        }
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }
 
    public class GroupIconConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var data = value != null ? value as Group : null;
            if (data != null)
            {
                SfDataGrid dataGrid = (SfDataGrid)parameter;
                if ((value as Group).Parent is TopLevelGroup)
                {
                    return "plus_icon_black.png";
                }
                else
                {
                    return "plus_icon_green.png";
                }
            }
            return null;
        }
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

public class CustomStyle : DataGridStyle
    {
        public override ImageSource GetGroupCollapseIcon()
        {
            return null;
        }
 
        public override ImageSource GetGroupExpanderIcon()
        {
            return null;
        }
 
        public override Color GetIndentBackgroundColor(RowType rowType)
        {
            return Color.White;
        }
    }