code: def download_previews(self, savedir=None):
          
          for obsid in self.obsids:
              pm = io.PathManager(obsid.img_id, savedir=savedir)
              pm.basepath.mkdir(exist_ok=True)
              basename = Path(obsid.medium_img_url).name
              print("Downloading", basename)
              urlretrieve(obsid.medium_img_url, str(pm.basepath / basename))
docs: Download preview files for the previously found and stored Opus obsids.
  
          Parameters
          ==========
          savedir: str or pathlib.Path, optional
              If the database root folder as defined by the config.ini should not be used,
              provide a different savedir here. It will be handed to PathManager.