code: def download_data(identifier, outdir):
      
      # determine target
      if use_local_data_repository is not None:
          url_base = 'file:' + request.pathname2url(
              use_local_data_repository + os.sep)
      else:
          url_base = repository_url
  
      print('url_base: {}'.format(url_base))
      url = url_base + inventory_filename
      # download inventory file
      filename, headers =request.urlretrieve(url)
  
      df = pd.read_csv(
          filename,
          delim_whitespace=True,
          comment='#',
          header=None,
          names=['identifier', 'rel_path'],
      )
  
      # find relative path to data file
      rel_path_query = df.query('identifier == "{}"'.format(identifier))
      if rel_path_query.shape[0] == 0:
          raise Exception('identifier not found')
      rel_path = rel_path_query['rel_path'].values[0]
  
      # download the file
      url = url_base + rel_path
      print('data url: {}'.format(url))
      filename, headers =request.urlretrieve(url)
  
      if not os.path.isdir(outdir):
          os.makedirs(outdir)
  
      zip_obj = zipfile.ZipFile(filename)
      zip_obj.extractall(outdir)
docs: Download data from a separate data repository for testing.
  
      Parameters
      ----------
      identifier: string
          The identifier used to find the data set
      outdir: string
          unzip the data in this directory