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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 preview(self):
 """ Blocking function. Opens OpenCV window to display stream. """

        win_name = 'Camera'
        cv2.namedWindow(win_name, cv2.WINDOW_AUTOSIZE)
        cv2.moveWindow(win_name,20,20)
        self.open()
        while(self.isOpened()):
            cv2.imshow(win_name,self._stream.read()[1])
            if cv2.waitKey(25) & 0xFF == ord('q'):
                break
        cv2.waitKey()
        cv2.destroyAllWindows()
        cv2.waitKey()