How to change the expander icon in WPF TreeGrid?

<Window.Resources>
    <Style TargetType="syncfusion:TreeGridExpander">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="syncfusion:TreeGridExpander">
                    <Grid Background="{TemplateBinding Background}"
                          SnapsToDevicePixels="True">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="ExpansionStates">
                                <VisualState x:Name="Collapsed" />
                                <VisualState x:Name="Expanded">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames 
                                            BeginTime="00:00:00"
                                            Duration="00:00:00"
                                            Storyboard.TargetName="PART_GridExpanderCellPath"
                                            Storyboard.TargetProperty="RenderTransform">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <RotateTransform Angle="0" />
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Path x:Name="PART_GridExpanderCellPath"
                              Width="10"
                              Height="10"
                              Margin="2,0,0,0"
                              HorizontalAlignment="Center"
                              VerticalAlignment="Center"
                              Fill="{TemplateBinding Foreground}"
Data="F1M1464.78,374.21C1466.31,374.21,1466.94,375.538,1466.17,376.861L1435.89,429.439C1435.12,430.759,1433.87,430.823,1433.11,429.5L1402.82,376.827C1402.06,375.507,1402.69,374.21,1404.21,374.21L1464.78,374.21"
                              SnapsToDevicePixels="True"
                              Stretch="Fill"
                              Stroke="{TemplateBinding Foreground}"
                              UseLayoutRounding="False">
                            <Path.RenderTransform>
                                <TransformGroup>
                                    <TransformGroup.Children>
                                        <RotateTransform Angle="270" 
                                                        CenterX="4" 
                                                        CenterY="4" />
                                    </TransformGroup.Children>
                                </TransformGroup>
                            </Path.RenderTransform>
                        </Path>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>