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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _load_new(self, img_data: str):
 """ Load a new image. :param img_data: the image data as a base64 string :return: None """

        self._image = tk.PhotoImage(data=img_data)
        self._image = self._image.subsample(int(200 / self._size),
                                            int(200 / self._size))
        self._canvas.delete('all')
        self._canvas.create_image(0, 0, image=self._image, anchor='nw')

        if self._user_click_callback is not None:
            self._user_click_callback(self._on)