How to use the kivymd.elevationbehavior.RectangularElevationBehavior function in kivymd

anchor_x: 'right'
            anchor_y: 'center'
            size_hint: 1, None
            height: dp(52) if len(root._action_buttons) > 0 else 0
            padding: dp(8), dp(8)
            GridLayout:
                id: action_area
                rows: 1
                size_hint: None, None if len(root._action_buttons) > 0 else 1
                height: dp(36) if len(root._action_buttons) > 0 else 0
                width: self.minimum_width
                spacing: dp(8)
''')


class MDDialog(ThemableBehavior, RectangularElevationBehavior, ModalView):
    title = StringProperty('')

    content = ObjectProperty(None)

    md_bg_color = ListProperty([0, 0, 0, .2])

    _container = ObjectProperty()
    _action_buttons = ListProperty([])
    _action_area = ObjectProperty()

    def __init__(self, **kwargs):
        super(MDDialog, self).__init__(**kwargs)
        self.bind(_action_buttons=self._update_action_buttons,
                  auto_dismiss=lambda *x: setattr(self.shadow, 'on_release',
                                                  self.shadow.dismiss if self.auto_dismiss else None))

class NavigationDrawerDivider(OneLineListItem):
    '''
    A small full-width divider that can be placed in the :class:`MDNavigationDrawer`
    '''
    disabled = True
    divider = None
    _txt_top_pad = NumericProperty(dp(8))
    _txt_bot_pad = NumericProperty(dp(8))

    def __init__(self, **kwargs):
        super(OneLineListItem, self).__init__(**kwargs)
        self.height = dp(16)


class MDNavigationDrawer(BoxLayout, ThemableBehavior, RectangularElevationBehavior):
    '''
    '''
    _elevation = NumericProperty(0)
    _header_container = ObjectProperty()
    _list = ObjectProperty()
    active_item = ObjectProperty(None)
    orientation = 'vertical'
    panel = ObjectProperty()
    shadow_color = ListProperty([0, 0, 0, 0])

    def __init__(self, **kwargs):
        super(MDNavigationDrawer, self).__init__(**kwargs)

    def add_widget(self, widget, index=0):
        '''
        If the widget is a subclass of :class:`~NavigationDrawerHeaderBase`, then it will be placed above the

text = StringProperty('')
    _capitalized_text = StringProperty('')

    def on_text(self, instance, value):
        self._capitalized_text = value.upper()


class MDIconButton(BaseRoundButton, BaseFlatButton, BasePressedButton):
    icon = StringProperty('checkbox-blank-circle')


class MDFlatButton(BaseRectangularButton, BaseFlatButton, BasePressedButton):
    pass


class MDRaisedButton(BaseRectangularButton, RectangularElevationBehavior,
                     BaseRaisedButton, BasePressedButton):
    pass


class MDFloatingActionButton(BaseRoundButton, CircularElevationBehavior,
                             BaseRaisedButton):
    icon = StringProperty('android')
    background_palette = StringProperty('Accent')

class ColorSelector(MDIconButton):
    color_name = OptionProperty(
            'Indigo',
            options=['Red', 'Pink', 'Purple', 'DeepPurple', 'Indigo', 'Blue',
                     'LightBlue', 'Cyan', 'Teal', 'Green', 'LightGreen',
                     'Lime', 'Yellow', 'Amber', 'Orange', 'DeepOrange',
                     'Brown', 'Grey', 'BlueGrey'])

    def rgb_hex(self, col):
        return get_color_from_hex(colors[col][self.theme_cls.accent_hue])


class MDThemePicker(ThemableBehavior, FloatLayout, ModalView,
                    SpecificBackgroundColorBehavior,
                    RectangularElevationBehavior):
    pass


if __name__ == "__main__":
    from kivy.app import App
    from kivymd.theming import ThemeManager

    class ThemePickerApp(App):
        theme_cls = ThemeManager()

        def build(self):
            main_widget = Builder.load_string("""
#:import MDRaisedButton kivymd.button.MDRaisedButton
#:import MDThemePicker kivymd.theme_picker.MDThemePicker
FloatLayout:
    MDRaisedButton:

MDFlatButton:
        width: dp(32)
        id: ok_button
        pos: root.pos[0]+root.size[0]-self.width-dp(10), root.pos[1] + dp(10)
        text: "OK"
        on_release: root.close_ok()
    MDFlatButton:
        id: cancel_button
        pos: root.pos[0]+root.size[0]-self.width-ok_button.width-dp(10), root.pos[1] + dp(10)
        text: "Cancel"
        on_release: root.close_cancel()
""")


class MDTimePicker(ThemableBehavior, FloatLayout, ModalView,
                   RectangularElevationBehavior):
    # md_bg_color = ListProperty((0, 0, 0, 0))
    time = ObjectProperty()

    def __init__(self, **kwargs):
        super(MDTimePicker, self).__init__(**kwargs)
        self.current_time = self.ids.time_picker.time

    def set_time(self, time):
        try:
            self.ids.time_picker.set_time(time)
        except AttributeError:
            raise TypeError(
                'MDTimePicker.set_time must receive a datetime object, '
                'not a "{}"'.format(type(time).__name__))

    def close_cancel(self):

font_style: 'Title'
            opposite_colors: root.opposite_colors
            theme_text_color: 'Custom'
            text_color: root.specific_text_color
            text: root.title
            shorten: True
            shorten_from: 'right'
    BoxLayout:
        id: right_actions
        orientation: 'horizontal'
        size_hint_x: None
        padding: [0, (self.height - dp(48))/2]
''')


class Toolbar(ThemableBehavior, RectangularElevationBehavior,
              SpecificBackgroundColorBehavior, BoxLayout):
    left_action_items = ListProperty()
    """The icons on the left of the Toolbar.

    To add one, append a list like the following:

        ['icon_name', callback]

    where 'icon_name' is a string that corresponds to an icon definition and
     callback is the function called on a touch release event.
    """

    right_action_items = ListProperty()
    """The icons on the left of the Toolbar.

    Works the same way as :attr:`left_action_items`

font_size: root._label_font_size
            pos_hint: {'center_x': .5, 'center_y': 0.6}

    canvas:
        Color:
            rgba: root.theme_cls.bg_normal
        Rectangle:
            size: root.size
""")


class MDTabBar(ThemableBehavior, BackgroundColorBehavior, BoxLayout):
    pass


class MDBottomNavigationBar(ThemableBehavior, BackgroundColorBehavior, FloatLayout, RectangularElevationBehavior):
    pass


class MDTabHeader(MDFlatButton):
    """ Internal widget for headers based on MDFlatButton"""

    width = BoundedNumericProperty(dp(0), min=dp(72), max=dp(264), errorhandler=lambda x: dp(72))
    tab = ObjectProperty(None)
    panel = ObjectProperty(None)


class MDBottomNavigationErrorCache:
    last_size_warning = 0


def small_error_warn(x):

class DayButton(ThemableBehavior, CircularRippleBehavior, ButtonBehavior,
                AnchorLayout):
    text = StringProperty()
    owner = ObjectProperty()
    is_today = BooleanProperty(False)
    is_selected = BooleanProperty(False)

    def on_release(self):
        self.owner.set_selected_widget(self)


class WeekdayLabel(MDLabel):
    pass


class MDDatePicker(FloatLayout, ThemableBehavior, RectangularElevationBehavior,
                   SpecificBackgroundColorBehavior, ModalView):
    _sel_day_widget = ObjectProperty()
    cal_list = None
    cal_layout = ObjectProperty()
    sel_year = NumericProperty()
    sel_month = NumericProperty()
    sel_day = NumericProperty()
    day = NumericProperty()
    month = NumericProperty()
    year = NumericProperty()
    today = date.today()
    callback = ObjectProperty()
    background_color = ListProperty([0, 0, 0, 0.7])

    class SetDateError(Exception):
        pass