community[patch]: callback before yield for _stream/_astream (#17907)

- Description: callback on_llm_new_token before yield chunk for
_stream/_astream for some chat models, make all chat models in a
consistent behaviour.
- Issue: N/A
- Dependencies: N/A

libs/community/langchain_community/chat_models/baichuan.py

@@ -219,9 +219,9 @@ class ChatBaichuan(BaseChatModel):
                 )
                 default_chunk_class = chunk.__class__
                 cg_chunk = ChatGenerationChunk(message=chunk)
-                yield cg_chunk
                 if run_manager:
                     run_manager.on_llm_new_token(chunk.content, chunk=cg_chunk)
+                yield cg_chunk
 
     def _chat(self, messages: List[BaseMessage], **kwargs: Any) -> requests.Response:
         parameters = {**self._default_params, **kwargs}