Add dolly prompt

Signed-off-by: junjie.jiang <junjie.jiang@zilliz.com>

__init__.py

@@ -1,4 +1,4 @@
 from .qa_prompt import QAPrompt
 
-def question_answer():
-    return QAPrompt()
+def question_answer(temp: str = None, llm_name: str = None):
+    return QAPrompt(temp, llm_name)

qa_prompt.py

@@ -3,10 +3,7 @@ from typing import List, Tuple, Dict, Optional
 from towhee.operator import PyOperator
 
 
-class QAPrompt(PyOperator):
-    def __init__(self):
-        super().__init__()
-        self._template = """Use the following pieces of context to answer the question at the end.
+gpt_prompt =  """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}
@@ -16,6 +13,24 @@ Question: {question}
 Helpful Answer:
 """
 
+dolly_prompt = """{question}
+
+Input:
+{context}
+"""
+
+
+class QAPrompt(PyOperator):
+    def __init__(self, temp: str = None, llm_name: str = None):
+        super().__init__()
+        if temp:
+            self._template = temp
+        else:
+            if llm_name.lower() == 'dolly':
+                self._template = dolly_prompt
+            else:
+                self._template = gpt_prompt
+
     def __call__(self, question: str, docs: List[str], history=Optional[List[Tuple]]) -> List[Dict[str, str]]:
         """
         history: