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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 off(self):
 """Send an OFF message to device group."""

        off_command = ExtendedSend(self._address,
                                   COMMAND_LIGHT_OFF_0X13_0X00,
                                   self._udata)
        off_command.set_checksum()
        self._send_method(off_command, self._off_message_received)