def read_plain_vocabulary(filename):
    """
    Read a vocabulary file containing one word type per line.
    Return a list of word types.
    """
    words = []
    with open(filename, 'rb') as f:
        for line in f:
            word = line.decode('utf-8').strip()
            if not word:
                continue
            words.append(word)
    
    return words