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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 close(self):
 """Closes the open J-Link. Args: self (JLink):
 the ``JLink`` instance Returns: ``None`` Raises: JLinkException: if there is no connected JLink. """

        self._dll.JLINKARM_Close()

        if self._lock is not None:
            del self._lock
            self._lock = None

        return None