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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_tracker(self, resource):
 """ Return the resource tracker that is tracking ``resource``. :param resource: A resource. :return: A resource tracker. :rtype: :class:`_ResourceTracker` """

        with self._lock:
            for rt in self._reference_queue:
                if rt is not None and resource is rt.resource:
                    return rt

        raise UnknownResourceError('Resource not created by pool')