docs: 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()