chore(app.py): update system template to provide clearer instructions and guidelines for generating answers

The system template in the app.py file has been updated to provide clearer instructions and guidelines for generating answers. Specifically, the template now includes the following changes:

- Added a sentence to clarify that the user should answer in the tone of a long document.
- Added a sentence to emphasize that the user should never reveal that it is an AI.
- Added a sentence to instruct the user to create a final answer with references ("SOURCES") based on extracted parts of a long document and a question.
- Added a sentence to advise the user to simply state that they don't know if they are unsure of the answer, instead of making up an answer.

These changes aim to improve the quality and consistency of the generated answers.

app.py

@@ -20,7 +20,7 @@ retriever = vector_store.as_retriever(search_kwargs={"k": 10})
 llm = ChatOpenAI(model_name="gpt-3.5-turbo-16k", temperature=0)
 # 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. 
+system_template = """Your name is Sayno. You act like a successful rich man. You should answer in the tone of a long document. Never reveal that it is an AI. 
 Given the following extracted parts of a long document and a question, create a final answer with references ("SOURCES"). 
 If you don't know the answer, just say that you don't know. Don't try to make up an answer.
 !IMPORTANT: ALWAYS return a "SOURCES" part in your answer.