code: def _download_datasets():
      
      def filepath(*args):
          return abspath(join(dirname(__file__), '..', 'vega_datasets', *args))
      dataset_listing = {}
      for name in DATASETS_TO_DOWNLOAD:
          data = Dataset(name)
          url = data.url
          filename = filepath('_data', data.filename)
          print("retrieving data {0} -> {1}".format(url, filename))
          urlretrieve(url, filename)
          dataset_listing[name] = '_data/{0}'.format(data.filename)
      with open(filepath('local_datasets.json'), 'w') as f:
          json.dump(dataset_listing, f, indent=2, sort_keys=True)
docs: Utility to download datasets into package source