import string

for example in train_data.examples:
    text = [x.lower() for x in vars(example)['text']] ------ 소문자로 변경
    text = [x.replace("<br","") for x in text] ------ “<br”을 “ ”(공백)으로 변경
    text = [''.join(c for c in s if c not in string.punctuation) for s in text] ------ 구두점 제거
    text = [s for s in text if s] ------ 공백 제거
    vars(example)['text'] = text

import random
train_data, valid_data = train_data.split(random_state=random.seed(0), split_ratio=0.8) ------ ①