Close threads associated to parent_id

def close_threads(self, parent):
        """Close threads associated to parent_id"""
        logger.debug("Call ThreadManager's 'close_threads'")
        if parent is None:
            # Closing all threads
            self.pending_threads = []
            threadlist = []
            for threads in list(self.started_threads.values()):
                threadlist += threads
        else:
            parent_id = id(parent)
            self.pending_threads = [(_th, _id) for (_th, _id)
                                    in self.pending_threads
                                    if _id != parent_id]
            threadlist = self.started_threads.get(parent_id, [])
        for thread in threadlist:
            logger.debug("Waiting for thread %r to finish" % thread)
            while thread.isRunning():
                # We can't terminate thread safely, so we simply wait...
                QApplication.processEvents()