Rotate an object in HelixViewport3D in a WPF app

I'm trying to show a 3d object in a WPF app using helixtoolkit and rotate it according to 3 variables (user inputs) along x,y,z axes. But i coudn't find a function in helix toolkit to to rotate the 3d object.

C# code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Media.Media3D;
using HelixToolkit.Wpf;

namespace HelixTrial
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            ModelImporter importer = new ModelImporter();
            Model3D model = importer.Load("D:\\Crate1.obj");
            Models.Content = model;

            // need to apply rotation to the model using three x,y,z variables
        }

    }
}

XAML code

<Window x:Class="HelixTrial.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:HelixToolkit="clr-namespace:HelixToolkit.Wpf;assembly=HelixToolkit.Wpf"
    Title="MainWindow" Height="500" Width="500">
    <Grid  Width="400" Height="400">
        <HelixToolkit:HelixViewport3D x:Name="Viewport" ZoomExtentsWhenLoaded="True">
            <HelixToolkit:SunLight/>
            <ModelVisual3D x:Name="Models"/>
        </HelixToolkit:HelixViewport3D>
    </Grid>
</Window>

You couldn't find it in the toolkit, because it's a standard WPF function. So in your example it would look somewhat like this:

<ModelVisual3D x:Name="Models">
    <ModelVisual3D.Transform>
        <Transform3DGroup>
            <RotateTransform3D>
                <RotateTransform3D.Rotation>
                     <AxisAngleRotation3D Axis="1,0,0" Angle="{Binding varX}"/>
                </RotateTransform3D.Rotation>
            </RotateTransform3D>
            <RotateTransform3D>
                <RotateTransform3D.Rotation>
                    <AxisAngleRotation3D Axis="0,1,0" Angle="{Binding varY}"/>
                </RotateTransform3D.Rotation>
            </RotateTransform3D>
            <RotateTransform3D>
                <RotateTransform3D.Rotation>
                     <AxisAngleRotation3D Axis="0,0,1" Angle="{Binding varZ}"/>
                </RotateTransform3D.Rotation>
            </RotateTransform3D>
        </Transform3DGroup>
    </ModelVisual3D.Transform>
</ModelVisual3D>