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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 unlock(self):
 """ Unlock the IOS-XR device config. Use if Locking/Unlocking is not performaed automatically by lock=False """

        if self.locked:
            rpc_command = '<Unlock/>'
            try:
                self._execute_rpc(rpc_command)
            except XMLCLIError:
                raise UnlockError('Unable to unlock the config!', self)
            self.locked = False