fix: wrong ConversationBufferMemory parameters

app.py

@@ -6,6 +6,7 @@ import spacy
 from langchain.chains import RetrievalQA, ConversationalRetrievalChain
 from langchain.memory import ConversationBufferMemory
 from langchain.text_splitter import SpacyTextSplitter
+from langchain_community.chat_message_histories import ChatMessageHistory
 from langchain_community.document_loaders import PyPDFLoader
 from langchain_community.embeddings import HuggingFaceInferenceAPIEmbeddings
 from langchain_community.vectorstores import Chroma
@@ -93,7 +94,9 @@ class RAGDemo(object):
 
     def _chat_qa(self, message, chat_history):
         memory = ConversationBufferMemory(
-            chat_memory=convert_chat_history_to_messages(chat_history),
+            chat_memory=ChatMessageHistory(
+                messages=convert_chat_history_to_messages(chat_history)
+            ),
             memory_key="chat_history",
             return_messages=True,
         )