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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_bundle_imported_services(self, bundle):
 """ Returns this bundle's ServiceReference list for all services it is using or returns None if this bundle is not using any services. A bundle is considered to be using a service if its use count for that service is greater than zero. The list is valid at the time of the call to this method, however, as the Framework is a very dynamic environment, services can be modified or unregistered at any time. :param bundle: The bundle to look into :return: The references of the services used by this bundle """

        with self.__svc_lock:
            return sorted(self.__bundle_imports.get(bundle, []))