Keep only Thai words with at least min_freq frequency
    and has length between min_len and max_len characters

def _keep(
    word_freq: int,
    min_freq: int,
    min_len: int,
    max_len: int,
    dict_filter: Callable[[str], bool],
):
    """
    Keep only Thai words with at least min_freq frequency
    and has length between min_len and max_len characters
    """
    if not word_freq or word_freq[1] < min_freq:
        return False

    word = word_freq[0]
    if not word or len(word) < min_len or len(word) > max_len or word[0] == ".":
        return False

    return dict_filter(word)