Add qa_prompt

__init__.py

@@ -0,0 +1,4 @@
+from .qa_prompt import QAPrompt
+
+def question_answer():
+    return QAPrompt()

qa_prompt.py

@@ -0,0 +1,29 @@
+from typing import List, Tuple, Dict
+
+
+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.
+
+{context}
+
+Question: {question}
+
+Helpful Answer:'
+"""
+
+    def __call__(self, question: str, docs: List[str], history=None) -> List[Dict[str, str]]:
+        context = '\n'.join(docs)
+        prompt_str = self._template.format(context=context, question=question)
+        ret = [{'question': prompt_str}]
+        if not isinstance(history, list):
+            return ret
+        else:
+            history_data = []
+            for item in history:
+                history_data.append({'question': item[0], 'answer': item[1]})
+            return history + ret