bert를 이용한 텍스트 분류 imdb 편 질문드립니다.

코드의 처음 부분에서 라이브러리 설치할 때,  

!pip install -q -u tensorflow-text 와

!pip install -q tf-models-official이 정상적으로 설치되었습니다.

이후 라이브러리를 import할 때 

import official.nlp 는 작동이 되지만,

from official.nlp import optimization은 

---------------------------------------------------------------------------

ImportError                               Traceback (most recent call last)

<ipython-input-31-2f06be8b9abc> in <module>()

      6 import tensorflow_text as text

      7 import official.nlp

----> 8 from official.nlp import optimization

      9 # to create AdamW optimizer

     10 import matplotlib.pyplot as plt

5 frames

/usr/local/lib/python3.7/dist-packages/keras/api/_v2/keras/backend/experimental/__init__.py in <module>()

      6 import sys as _sys

      7

----> 8 from keras.backend import disable_tf_random_generator

      9 from keras.backend import enable_tf_random_generator

     10 from keras.backend import is_tf_random_generator_enabled

ImportError: cannot import name 'disable_tf_random_generator' from 'keras.backend' (/usr/local/lib/python3.7/dist-packages/keras/backend.py)

---------------------------------------------------------------------------

NOTE: If your import is failing due to a missing package, you can

manually install dependencies using either !pip or !apt.

To view examples of installing some common dependencies, click the

"Open Examples" button below.

이런 에러를 발생시키고 있습니다.

colab 설치 폴더에서 확인해봐도, 문제 없이 잘 깔려있고, 심지어 optimazation.py파일도 잘 있는데

왜 import 되지 않는 걸까요..?