examples/legacy/run_chinese_ref.py/add_sub_symbol
def add_sub_symbol(bert_tokens: List[str], chinese_word_set: set()):
    if not chinese_word_set:
        return bert_tokens
    max_word_len = max([len(w) for w in chinese_word_set])

    bert_word = bert_tokens
    start, end = 0, len(bert_word)
    while start < end:
        single_word = True
        if is_chinese(bert_word[start]):
            l = min(end - start, max_word_len)
            for i in range(l, 1, -1):
                whole_word = "".join(bert_word[start : start + i])
                if whole_word in chinese_word_set:
                    for j in range(start + 1, start + i):
                        bert_word[j] = "##" + bert_word[j]
                    start = start + i
                    single_word = False
                    break
        if single_word:
            start += 1
    return bert_word