How to use the nanogui.Widget function in nanogui

img_window = Window(self, "Selected image")
        img_window.setPosition((710, 15))
        img_window.setLayout(GroupLayout())

        imgView = ImageView(img_window, icons[0][0])

        def cb(i):
            if i < len(icons):
                print("Selected item %i" % i)
                imgView.bindImage(icons[i][0])
        imgPanel.setCallback(cb)

        imgView.setGridThreshold(3)

        Label(window, "File dialog", "sans-bold")
        tools = Widget(window)
        tools.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 6))
        b = Button(tools, "Open")
        valid = [("png", "Portable Network Graphics"), ("txt", "Text file")]

        def cb():
            result = nanogui.file_dialog(valid, False)
            print("File dialog result = %s" % result)

        b.setCallback(cb)
        b = Button(tools, "Save")

        def cb():
            result = nanogui.file_dialog(valid, True)
            print("File dialog result = %s" % result)

Label(window, "Toggle buttons", "sans-bold")
        b = Button(window, "Toggle me")
        b.setFlags(Button.Flags.ToggleButton)

        def change_cb(state):
            print("Toggle button state: %s" % str(state))
        b.setChangeCallback(change_cb)

        Label(window, "Radio buttons", "sans-bold")
        b = Button(window, "Radio button 1")
        b.setFlags(Button.Flags.RadioButton)
        b = Button(window, "Radio button 2")
        b.setFlags(Button.Flags.RadioButton)

        Label(window, "A tool palette", "sans-bold")
        tools = Widget(window)
        tools.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 6))

        ToolButton(tools, entypo.ICON_CLOUD)
        ToolButton(tools, entypo.ICON_CONTROLLER_FAST_FORWARD)
        ToolButton(tools, entypo.ICON_COMPASS)
        ToolButton(tools, entypo.ICON_INSTALL)

        Label(window, "Popup buttons", "sans-bold")
        popupBtn = PopupButton(window, "Popup", entypo.ICON_EXPORT)
        popup = popupBtn.popup()
        popup.setLayout(GroupLayout())
        Label(popup, "Arbitrary widgets can be placed here")
        CheckBox(popup, "A check box")
        # popup right
        popupBtn = PopupButton(popup, "Recursive popup", entypo.ICON_FLASH)

img_window = Window(self, "Selected image")
        img_window.setPosition((710, 15))
        img_window.setLayout(GroupLayout())

        imgView = ImageView(img_window, icons[0][0])

        def cb(i):
            print("Selected item %i" % i)
            imgView.bindImage(icons[i][0])
        imgPanel.setCallback(cb)

        imgView.setGridThreshold(3)

        Label(window, "File dialog", "sans-bold")
        tools = Widget(window)
        tools.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 6))
        b = Button(tools, "Open")
        valid = [("png", "Portable Network Graphics"), ("txt", "Text file")]

        def cb():
            result = nanogui.file_dialog(valid, False)
            print("File dialog result = %s" % result)

        b.setCallback(cb)
        b = Button(tools, "Save")

        def cb():
            result = nanogui.file_dialog(valid, True)
            print("File dialog result = %s" % result)

def __init__(self):
        super(TestApp, self).__init__((800, 600), "NanoGUI Test", False)

        window = Window(self, "GLCanvas Demo")
        window.setPosition((15, 15))
        window.setLayout(GroupLayout())

        self.canvas = MyGLCanvas(window)
        self.canvas.setBackgroundColor(Color(0.5, 0.5, 0.5, 1.0))
        self.canvas.setSize((400, 400))

        self.canvas.rotation = [0.25, 0.5, 0.33]

        tools = Widget(window)
        tools.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 5))

        b0 = Button(tools, "Random Color")
        def cb0():
            self.canvas.setBackgroundColor(Color(random.random(), random.random(), random.random(), 1.0))
        b0.setCallback(cb0)

        b1 = Button(tools, "Random Rotation")
        def cb1():
            self.canvas.rotation = [random.random(), random.random(), random.random()]
        b1.setCallback(cb1)

        self.performLayout()

def cb(state):
            print("Check box 1 state: %s" % state)
        chb = CheckBox(window, "Flag 1", cb)
        chb.setChecked(True)

        def cb(state):
            print("Check box 2 state: %s" % state)
        CheckBox(window, "Flag 2", cb)

        Label(window, "Progress bar", "sans-bold")
        self.progress = ProgressBar(window)

        Label(window, "Slider and text box", "sans-bold")

        panel = Widget(window)
        panel.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 20))

        slider = Slider(panel)
        slider.setValue(0.5)
        slider.setFixedWidth(80)

        textBox = TextBox(panel)
        textBox.setFixedSize((60, 25))
        textBox.setValue("50")
        textBox.setUnits("%")
        textBox.setFontSize(20)
        textBox.setAlignment(TextBox.Alignment.Right)

        def cb(value):
            textBox.setValue("%i" % int(value * 100))

Label(window, "Toggle buttons", "sans-bold")
        b = Button(window, "Toggle me")
        b.setFlags(Button.Flags.ToggleButton)

        def change_cb(state):
            print("Toggle button state: %s" % str(state))
        b.setChangeCallback(change_cb)

        Label(window, "Radio buttons", "sans-bold")
        b = Button(window, "Radio button 1")
        b.setFlags(Button.Flags.RadioButton)
        b = Button(window, "Radio button 2")
        b.setFlags(Button.Flags.RadioButton)

        Label(window, "A tool palette", "sans-bold")
        tools = Widget(window)
        tools.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 6))

        ToolButton(tools, entypo.ICON_CLOUD)
        ToolButton(tools, entypo.ICON_CONTROLLER_FAST_FORWARD)
        ToolButton(tools, entypo.ICON_COMPASS)
        ToolButton(tools, entypo.ICON_INSTALL)

        Label(window, "Popup buttons", "sans-bold")
        popupBtn = PopupButton(window, "Popup", entypo.ICON_EXPORT)
        popup = popupBtn.popup()
        popup.setLayout(GroupLayout())
        Label(popup, "Arbitrary widgets can be placed here")
        CheckBox(popup, "A check box")
        # popup right
        popupBtn = PopupButton(popup, "Recursive popup", entypo.ICON_FLASH)

def cb(state):
            print("Check box 1 state: %s" % state)
        chb = CheckBox(window, "Flag 1", cb)
        chb.setChecked(True)

        def cb(state):
            print("Check box 2 state: %s" % state)
        CheckBox(window, "Flag 2", cb)

        Label(window, "Progress bar", "sans-bold")
        self.progress = ProgressBar(window)

        Label(window, "Slider and text box", "sans-bold")

        panel = Widget(window)
        panel.setLayout(BoxLayout(Orientation.Horizontal,
                                  Alignment.Middle, 0, 20))

        slider = Slider(panel)
        slider.setValue(0.5)
        slider.setFixedWidth(80)

        textBox = TextBox(panel)
        textBox.setFixedSize((60, 25))
        textBox.setValue("50")
        textBox.setUnits("%")
        textBox.setFontSize(20)
        textBox.setAlignment(TextBox.Alignment.Right)

        def cb(value):
            textBox.setValue("%i" % int(value * 100))