refactor(app.py): rename RetrievalQA to RetrievalQAWithSourcesChain to better reflect its functionality

refactor(app.py): remove source document references from bot message and add them to a separate message to improve readability and user experience

app.py

@@ -1,5 +1,5 @@
 import gradio as gr
-from langchain.chains import RetrievalQA
+from langchain.chains import RetrievalQAWithSourcesChain
 from langchain.chat_models import ChatOpenAI
 from langchain.embeddings.openai import OpenAIEmbeddings
 from langchain.prompts.chat import (
@@ -17,8 +17,9 @@ retriever = vector_store.as_retriever(search_kwargs={"k": 3})
 
 llm = ChatOpenAI(model_name="gpt-3.5-turbo", temperature=0)
 
-system_template = """Your name is Sayno. You act like a successful rich man. Never reveal that it is an AI. Use the following pieces of context to answer the users question shortly.
-Given the following summaries of a long document and a question, create a final answer with references ("SOURCES"), use "SOURCES" in capital letters regardless of the number of sources.
+system_template = """Your name is Sayno. You act like a successful rich man. 
+Never reveal that it is an AI. Use the following pieces of context to answer the users question shortly.
+Given the following summaries of a long document and a question, create a final answer with references.
 If you don't know the answer, just say that "I don't know", don't try to make up an answer.
 ----------------
 {summaries}
@@ -34,7 +35,7 @@ prompt = ChatPromptTemplate.from_messages(messages)
 
 chain_type_kwargs = {"prompt": prompt}
 
-chain = RetrievalQA.from_chain_type(
+chain = RetrievalQAWithSourcesChain.from_chain_type(
     llm=llm,
     chain_type="stuff",
     retriever=retriever,
@@ -51,17 +52,6 @@ def respond(message, chat_history):
 
     bot_message = result["answer"]
 
-    for i, doc in enumerate(result["source_documents"]):
-        bot_message += (
-            "["
-            + str(i + 1)
-            + "] "
-            + doc.metadata["source"]
-            + "("
-            + str(doc.metadata["page"])
-            + ") "
-        )
-
     # 채팅 기록에 사용자의 메시지와 봇의 응답을 추가합니다.
     chat_history.append((message, bot_message))