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.

def _cache_lookup(word, data_dir, native=False):
    """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.
    """
    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