feat: return document from conversation chain

app.py

@@ -38,19 +38,23 @@ def initialize_session_state():
         )
 
         memory = ConversationBufferMemory(
-            memory_key="chat_history", return_messages=True
+            output_key="answer", memory_key="chat_history", return_messages=True
         )
         st.session_state.conversation = ConversationalRetrievalChain.from_llm(
-            llm=llm, retriever=retriever, verbose=True, memory=memory
+            llm=llm,
+            retriever=retriever,
+            verbose=True,
+            memory=memory,
+            return_source_documents=True,
         )
 
 
 def on_click_callback():
     with get_openai_callback() as cb:
         human_prompt = st.session_state.human_prompt
-        llm_response = st.session_state.conversation.run(human_prompt)
+        llm_response = st.session_state.conversation(human_prompt)
         st.session_state.history.append(Message("human", human_prompt))
-        st.session_state.history.append(Message("ai", llm_response))
+        st.session_state.history.append(Message("ai", llm_response["answer"]))
         st.session_state.token_count += cb.total_tokens