fix API

Former-commit-id: 9b10c9a12e33ab897056ecc61d977d221c19141b

src/llmtuner/api/app.py

@@ -1,4 +1,3 @@
-import json
 import uvicorn
 from fastapi import FastAPI, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
@@ -96,7 +95,7 @@ def create_app():
             finish_reason=None
         )
         chunk = ChatCompletionStreamResponse(model=request.model, choices=[choice_data])
-        yield json.dumps(chunk, ensure_ascii=False)
+        yield chunk.json(exclude_unset=True, ensure_ascii=False)
 
         for new_text in chat_model.stream_chat(
             query, history, prefix, temperature=request.temperature, top_p=request.top_p, max_new_tokens=request.max_tokens
@@ -110,7 +109,7 @@ def create_app():
                 finish_reason=None
             )
             chunk = ChatCompletionStreamResponse(model=request.model, choices=[choice_data])
-            yield json.dumps(chunk, ensure_ascii=False)
+            yield chunk.json(exclude_unset=True, ensure_ascii=False)
 
         choice_data = ChatCompletionResponseStreamChoice(
             index=0,
@@ -118,7 +117,7 @@ def create_app():
             finish_reason=Finish.STOP
         )
         chunk = ChatCompletionStreamResponse(model=request.model, choices=[choice_data])
-        yield json.dumps(chunk, ensure_ascii=False)
+        yield chunk.json(exclude_unset=True, ensure_ascii=False)
         yield "[DONE]"
 
     return app