Fix bug

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

qa_prompt.py

@@ -4,16 +4,14 @@ from typing import List, Tuple, Dict, Optional
 class QAPrompt:
     def __init__(self):
         super().__init__()
-        self._template = """
-'Use the following pieces of context to answer the question at the end.
-If you don''t know the answer, just say that you don''t know, don''t try to make
-up an answer.
+        self._template = """Use the following pieces of context to answer the question at the end.
+If you don't know the answer, just say that you don't know, don't try to make up an answer.
 
 {context}
 
 Question: {question}
 
-Helpful Answer:'
+Helpful Answer:
 """
 
     def __call__(self, question: str, docs: List[str], history=Optional[List[Tuple]]) -> List[Dict[str, str]]:
@@ -30,4 +28,4 @@ Helpful Answer:'
             history_data = []
             for item in history:
                 history_data.append({'question': item[0], 'answer': item[1]})
-            return history + ret
+            return history_data + ret