code: def _cache_lookup(word, data_dir, native=False):
      
      trans_dir = "translations"
      if native:
          trans_dir += "_native"
      logger.debug("Cache lookup: %s", word)
      filename = data_dir.joinpath(trans_dir, "{}.html".format(word))
      if filename.is_file():
          with open(filename, mode="r") as f:
              logger.debug("Cache found: %s", word)
              # TODO: not sure if we should parse data here
              translation = _parse_cached(f.read())
              return translation
      logger.debug("Cache miss: %s", word)
      return None
docs: Checks if word is in cache.
  
      Parameters
      ----------
      word : str
          Word to check in cache.
      data_dir : pathlib.Path
          Cache directory location.
  
      Returns
      -------
      translation : str or None
          Translation of given word.