Write word to history file.

    Parameters
    ----------
    word : str
        Word to save to history.
    data_dir : pathlib.Path
        Directory where history file should be saved.

    data_dir and it's parent directories will be created if needed.

def _save_to_history(word, data_dir):
    """Write word to history file.

    Parameters
    ----------
    word : str
        Word to save to history.
    data_dir : pathlib.Path
        Directory where history file should be saved.

    data_dir and it's parent directories will be created if needed.
    """
    if not data_dir.exists():
        logger.debug("Creating DATA DIR: %s", data_dir.as_posix())
        data_dir.mkdir(parents=True)
    if word not in _get_words(data_dir):
        with open(data_dir.joinpath("words.txt"), mode="a+") as f:
            logger.debug("Adding to history: %s", word)
            f.write(word + "\n")