Update palmapi.py

palmapi.py

@@ -25,17 +25,28 @@ class PaLMChatPromptFmt(PromptFmt):
     @classmethod
     def prompt(cls, pingpong, truncate_size):
         ping = pingpong.ping[:truncate_size]
-        pong = "" if pingpong.pong is None else pingpong.pong[:truncate_size]
-        return [
-            {
-                "author": "USER",
-                "content": ping
-            },
-            {
-                "author": "AI",
-                "content": pong
-            },
-        ]
+        pong = pingpong.pong
+        
+        if pong is None:
+            return [
+                {
+                    "author": "USER",
+                    "content": ping
+                },
+            ]
+        else:
+            pong = pong[:truncate_size]
+
+            return [
+                {
+                    "author": "USER",
+                    "content": ping
+                },
+                {
+                    "author": "AI",
+                    "content": pong
+                },
+            ]
 
 class PaLMChatPPManager(PPManager):
     def build_prompts(self, from_idx: int=0, to_idx: int=-1, fmt: PromptFmt=PaLMChatPromptFmt, truncate_size: int=None):