Update chain.py

chain.py

@@ -139,7 +139,7 @@ Answer in Markdown:"""
 
 def _get_chat_history(chat_history: List[Tuple[str, str]]):
     buffer = ""
-    for human_s, ai_s in chat_history[-2:]:
+    for human_s, ai_s in chat_history[-1:]:
         human = f"Human: " + human_s
         ai = f"Assistant: " + ai_s
         buffer += "\n" + "\n".join([human, ai])