自定义langchain文档分割器时报错找不到 langchain.schema 模块

langchain==0.0.20
from langchain.schema import messages_to_dict
----> 1 from langchain.schema import DocumentModuleNotFoundError: No module named 'langchain.schema'

解决办法

pip install -U langchain

参考： https://github.com/langchain-ai/langchain/issues/8843