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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 clean_old_entries():
 """Deletes obsolete entries from the queues"""

    from indico_livesync.plugin import LiveSyncPlugin
    from indico_livesync.models.queue import LiveSyncQueueEntry

    queue_entry_ttl = LiveSyncPlugin.settings.get('queue_entry_ttl')
    if not queue_entry_ttl:
        return
    expire_threshold = now_utc() - timedelta(days=queue_entry_ttl)
    LiveSyncQueueEntry.find(LiveSyncQueueEntry.processed,
                            LiveSyncQueueEntry.timestamp < expire_threshold).delete(synchronize_session='fetch')