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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 get_preview(self):
 """ Get a preview from the camera's viewport. This will usually be a JPEG image with the dimensions depending on the camera. You will need to call the exit() method manually after you are done capturing a live preview. :return: The preview image as a bytestring :rtype: bytes """

        lib.gp_camera_capture_preview(self._cam, self.__camfile_p[0], self._ctx)
        lib.gp_file_get_data_and_size(self.__camfile_p[0], self.__data_p, self.__length_p)
        return ffi.buffer(self.__data_p[0], self.__length_p[0])[:]