code: def download_url(url, back_off=True, **kwargs):
      
      if back_off:
          return _download_with_backoff(url, as_file=True, **kwargs)
      else:
          return _download_without_backoff(url, as_file=True, **kwargs)
docs: Get the content of a URL and return a file-like object.
      back_off=True provides retry