docs: def url_to_fn(url):
      """
      Convert `url` to filename used to download the datasets.
  
      ``http://kitakitsune.org/xe`` -> ``kitakitsune.org_xe``.
  
      Args:
          url (str): URL of the resource.
  
      Returns:
          str: Normalized URL.
      """
      url = url.replace("http://", "").replace("https://", "")
      url = url.split("?")[0]
  
      return url.replace("%", "_").replace("/", "_")