code: def filename_to_url(filename: str) -> Tuple[str, str]:
      
      try:
          # If there is an etag, it's everything after the first period
          decoded, etag = filename.split(".", 1)
      except ValueError:
          # Otherwise, use None
          decoded, etag = filename, None
  
      filename_bytes = decoded.encode('utf-8')
      url_bytes = base64.b64decode(filename_bytes)
      return url_bytes.decode('utf-8'), etag
docs: Recovers the the url from the encoded filename. Returns it and the ETag
      (which may be ``None``)