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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 killall(self, everywhere=False):
 """Kills all nailgun servers started by pants. :param bool everywhere: If ``True``, kills all pants-started nailguns on this machine; otherwise restricts the nailguns killed to those started for the current build root. """

    with self._NAILGUN_KILL_LOCK:
      for proc in self._iter_nailgun_instances(everywhere):
        logger.info('killing nailgun server pid={pid}'.format(pid=proc.pid))
        proc.terminate()