How to use the napari.layers.shapes._constants.Mode function in napari

self._drag_start = None
        self._drag_box = None
        self._is_selecting = False
        self._fixed_vertex = None
        self._value = (None, None)
        self._moving_value = (None, None)
        if self._is_creating is True and self._mode == Mode.ADD_PATH:
            vertices = self._data_view.displayed_vertices[
                self._data_view.displayed_index == index
            ]
            if len(vertices) <= 2:
                self._data_view.remove(index)
            else:
                data_full = self.expand_shape(vertices)
                self._data_view.edit(index, data_full[:-1])
        if self._is_creating is True and self._mode == Mode.ADD_POLYGON:
            vertices = self._data_view.displayed_vertices[
                self._data_view.displayed_index == index
            ]
            if len(vertices) <= 2:
                self._data_view.remove(index)
        self._is_creating = False
        self._update_dims()

vertices = self._data_view.displayed_vertices[indices]
                        vertices[vertex] = coord
                        data_full = self.expand_shape(vertices)
                        self._data_view.edit(
                            index, data_full, new_type=new_type
                        )
                        shapes = self.selected_data
                        self._selected_box = self.interaction_box(shapes)
                        self.refresh()
            else:
                self._is_selecting = True
                if self._drag_start is None:
                    self._drag_start = coord
                self._drag_box = np.array([self._drag_start, coord])
                self._set_highlight()
        elif self._mode in [Mode.VERTEX_INSERT, Mode.VERTEX_REMOVE]:
            if len(self.selected_data) > 0:
                pass
            else:
                self._is_selecting = True
                if self._drag_start is None:
                    self._drag_start = coord
                self._drag_box = np.array([self._drag_start, coord])
                self._set_highlight()

def _finish_drawing(self):
        """Reset properties used in shape drawing."""
        index = copy(self._moving_value[0])
        self._is_moving = False
        self.selected_data = []
        self._drag_start = None
        self._drag_box = None
        self._is_selecting = False
        self._fixed_vertex = None
        self._value = (None, None)
        self._moving_value = (None, None)
        if self._is_creating is True and self._mode == Mode.ADD_PATH:
            vertices = self._data_view.displayed_vertices[
                self._data_view.displayed_index == index
            ]
            if len(vertices) <= 2:
                self._data_view.remove(index)
            else:
                data_full = self.expand_shape(vertices)
                self._data_view.edit(index, data_full[:-1])
        if self._is_creating is True and self._mode == Mode.ADD_POLYGON:
            vertices = self._data_view.displayed_vertices[
                self._data_view.displayed_index == index
            ]
            if len(vertices) <= 2:
                self._data_view.remove(index)
        self._is_creating = False
        self._update_dims()

self._selected_data_history = []
        self._selected_box = None

        self._drag_start = None
        self._fixed_vertex = None
        self._fixed_aspect = False
        self._aspect_ratio = 1
        self._is_moving = False
        self._fixed_index = 0
        self._is_selecting = False
        self._drag_box = None
        self._drag_box_stored = None
        self._is_creating = False
        self._clipboard = {}

        self._mode = Mode.PAN_ZOOM
        self._mode_history = self._mode
        self._status = self.mode
        self._help = 'enter a selection mode to edit shape properties'

        self.events.deselect.connect(lambda x: self._finish_drawing())
        self.events.face_color.connect(lambda e: self._update_thumbnail())
        self.events.edge_color.connect(lambda e: self._update_thumbnail())

        self.add(
            data,
            shape_type=shape_type,
            edge_width=edge_width,
            edge_color=edge_color,
            face_color=face_color,
            opacity=opacity,
            z_index=z_index,

def set_mode(self, event):
        mode = event.mode
        if mode == Mode.SELECT:
            self.select_button.setChecked(True)
        elif mode == Mode.DIRECT:
            self.direct_button.setChecked(True)
        elif mode == Mode.PAN_ZOOM:
            self.panzoom_button.setChecked(True)
        elif mode == Mode.ADD_RECTANGLE:
            self.rectangle_button.setChecked(True)
        elif mode == Mode.ADD_ELLIPSE:
            self.ellipse_button.setChecked(True)
        elif mode == Mode.ADD_LINE:
            self.line_button.setChecked(True)
        elif mode == Mode.ADD_PATH:
            self.path_button.setChecked(True)
        elif mode == Mode.ADD_POLYGON:
            self.polygon_button.setChecked(True)
        elif mode == Mode.VERTEX_INSERT:
            self.vertex_insert_button.setChecked(True)
        elif mode == Mode.VERTEX_REMOVE:

def _move(self, coord):
        """Moves object at given mouse position and set of indices.

        Parameters
        ----------
        coord : sequence of two int
            Position of mouse cursor in image coordinates.
        """
        vertex = self._moving_value[1]
        if self._mode in (
            [Mode.SELECT, Mode.ADD_RECTANGLE, Mode.ADD_ELLIPSE, Mode.ADD_LINE]
        ):
            if len(self.selected_data) > 0:
                self._is_moving = True
                if vertex is None:
                    # Check where dragging box from to move whole object
                    if self._drag_start is None:
                        center = self._selected_box[Box.CENTER]
                        self._drag_start = coord - center
                    center = self._selected_box[Box.CENTER]
                    shift = coord - center - self._drag_start
                    for index in self.selected_data:
                        self._data_view.shift(index, shift)
                    self._selected_box = self._selected_box + shift
                    self.refresh()
                elif vertex < Box.LEN:
                    # Corner / edge vertex is being dragged so resize object

def mode(self, mode):
        if isinstance(mode, str):
            mode = Mode(mode)

        if not self.editable:
            mode = Mode.PAN_ZOOM

        if mode == self._mode:
            return
        old_mode = self._mode
        if mode == Mode.PAN_ZOOM:
            self.cursor = 'standard'
            self.interactive = True
            self.help = 'enter a selection mode to edit shape properties'
        elif mode in [Mode.SELECT, Mode.DIRECT]:
            self.cursor = 'pointing'
            self.interactive = False
            self.help = (
                'hold  to pan/zoom, '

def set_mode(self, event):
        mode = event.mode
        if mode == Mode.SELECT:
            self.select_button.setChecked(True)
        elif mode == Mode.DIRECT:
            self.direct_button.setChecked(True)
        elif mode == Mode.PAN_ZOOM:
            self.panzoom_button.setChecked(True)
        elif mode == Mode.ADD_RECTANGLE:
            self.rectangle_button.setChecked(True)
        elif mode == Mode.ADD_ELLIPSE:
            self.ellipse_button.setChecked(True)
        elif mode == Mode.ADD_LINE:
            self.line_button.setChecked(True)
        elif mode == Mode.ADD_PATH:
            self.path_button.setChecked(True)
        elif mode == Mode.ADD_POLYGON:
            self.polygon_button.setChecked(True)
        elif mode == Mode.VERTEX_INSERT:
            self.vertex_insert_button.setChecked(True)
        elif mode == Mode.VERTEX_REMOVE:
            self.vertex_remove_button.setChecked(True)
        else:
            raise ValueError("Mode not recongnized")

def hold_to_pan_zoom(layer):
    """Hold to pan and zoom in the viewer."""
    if layer._mode != Mode.PAN_ZOOM:
        # on key press
        prev_mode = layer.mode
        prev_selected = layer.selected_data.copy()
        layer.mode = Mode.PAN_ZOOM

        yield

        # on key release
        layer.mode = prev_mode
        layer.selected_data = prev_selected
        layer._set_highlight()

def __init__(self, layer):
        super().__init__(layer)

        self.layer.events.mode.connect(self.set_mode)

        self.select_button = QtModeButton(
            layer, 'select', Mode.SELECT, 'Select mode'
        )
        self.direct_button = QtModeButton(
            layer, 'direct', Mode.DIRECT, 'Direct select mode'
        )
        self.panzoom_button = QtModeButton(
            layer, 'zoom', Mode.PAN_ZOOM, 'Pan/zoom mode'
        )
        self.rectangle_button = QtModeButton(
            layer, 'rectangle', Mode.ADD_RECTANGLE, 'Add rectangles'
        )
        self.ellipse_button = QtModeButton(
            layer, 'ellipse', Mode.ADD_ELLIPSE, 'Add ellipses'
        )
        self.line_button = QtModeButton(
            layer, 'line', Mode.ADD_LINE, 'Add lines'
        )