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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 download_items(cache_fn, start=None):
 """ Open the `cache_fn` as database and download all not-yet downloaded items. Args: cache_fn (str):
 Path to the sqlite database. If not exists, it will be created. start (int, default None):
 If set, start from this sysno. """

    with SqliteDict(cache_fn) as db:
        last_id = db.get("last_id", 0) if not start else start
        _download_items(db, last_id)
        db.commit()