code: def test_download(self):
      url = "https://s3-ap-northeast-1.amazonaws.com/dev.tech-sketch.jp/chakki/public/conll2003_en.zip"
      weights_file, params_file, preprocessor_file = download(url)
  
      self.assertTrue(os.path.exists(weights_file))
      self.assertTrue(os.path.exists(params_file))
      self.assertTrue(os.path.exists(preprocessor_file))
  
file_path: anago/tests/test_utils.py
imports: import os
  import unittest
  from anago.utils import load_data_and_labels, Vocabulary, download, NERSequence
  from anago.preprocessing import IndexTransformer
label_desc: Use image node_id 4 for calling the TestUtils obj's underlying member method code with example usage: obj.test_download() without return types