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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 unused_by(self, bundle):
 """ Indicates that this reference is not being used anymore by the given bundle. This method should only be used by the framework. :param bundle: A bundle that used this reference """

        if bundle is None or bundle is self.__bundle:
            # Ignore
            return

        with self.__usage_lock:
            try:
                if not self.__using_bundles[bundle].dec():
                    # This bundle has cleaner all of its usages of this
                    # reference
                    del self.__using_bundles[bundle]
            except KeyError:
                # Ignore error
                pass