Update summarizer_app.py

summarizer_app.py

@@ -1,6 +1,7 @@
 import os
 import json
-from langchain import OpenAI, ChatOpenAI, PromptTemplate, LLMChain
+from langchain import OpenAI, PromptTemplate, LLMChain
+from langchain.chat_models import ChatOpenAI
 from langchain.text_splitter import CharacterTextSplitter
 from langchain.chains.mapreduce import MapReduceChain
 from langchain.prompts import PromptTemplate