feat: Implement ChatBaichuan asynchronous interface (#23589)

- **Description:** Add interface to `ChatBaichuan` to support
asynchronous requests
    - `_agenerate` method
    - `_astream` method

---------

Co-authored-by: ccurme <chester.curme@gmail.com>

libs/community/langchain_community/chat_models/baichuan.py

@@ -1,11 +1,16 @@
 import json
 import logging
-from typing import Any, Dict, Iterator, List, Mapping, Optional, Type
+from contextlib import asynccontextmanager
+from typing import Any, AsyncIterator, Dict, Iterator, List, Mapping, Optional, Type
 
 import requests
-from langchain_core.callbacks import CallbackManagerForLLMRun
+from langchain_core.callbacks import (
+    AsyncCallbackManagerForLLMRun,
+    CallbackManagerForLLMRun,
+)
 from langchain_core.language_models.chat_models import (
     BaseChatModel,
+    agenerate_from_stream,
     generate_from_stream,
 )
 from langchain_core.messages import (
@@ -71,6 +76,27 @@ def _convert_delta_to_message_chunk(
         return default_class(content=content)  # type: ignore[call-arg]
 
 
+@asynccontextmanager
+async def aconnect_httpx_sse(
+    client: Any, method: str, url: str, **kwargs: Any
+) -> AsyncIterator:
+    """Async context manager for connecting to an SSE stream.
+
+    Args:
+        client: The httpx client.
+        method: The HTTP method.
+        url: The URL to connect to.
+        kwargs: Additional keyword arguments to pass to the client.
+
+    Yields:
+        An EventSource object.
+    """
+    from httpx_sse import EventSource
+
+    async with client.stream(method, url, **kwargs) as response:
+        yield EventSource(response)
+
+
 class ChatBaichuan(BaseChatModel):
     """Baichuan chat models API by Baichuan Intelligent Technology.
 
@@ -199,7 +225,7 @@ class ChatBaichuan(BaseChatModel):
         run_manager: Optional[CallbackManagerForLLMRun] = None,
         **kwargs: Any,
     ) -> Iterator[ChatGenerationChunk]:
-        res = self._chat(messages, **kwargs)
+        res = self._chat(messages, stream=True, **kwargs)
         if res.status_code != 200:
             raise ValueError(f"Error from Baichuan api response: {res}")
         default_chunk_class = AIMessageChunk
@@ -222,14 +248,96 @@ class ChatBaichuan(BaseChatModel):
                     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}
+    async def _agenerate(
+        self,
+        messages: List[BaseMessage],
+        stop: Optional[List[str]] = None,
+        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
+        stream: Optional[bool] = None,
+        **kwargs: Any,
+    ) -> ChatResult:
+        should_stream = stream if stream is not None else self.streaming
+        if should_stream:
+            stream_iter = self._astream(
+                messages, stop=stop, run_manager=run_manager, **kwargs
+            )
+            return await agenerate_from_stream(stream_iter)
 
-        model = parameters.pop("model")
-        headers = parameters.pop("headers", {})
+        headers = self._create_headers_parameters(**kwargs)
+        payload = self._create_payload_parameters(messages, **kwargs)
+
+        import httpx
+
+        async with httpx.AsyncClient(
+            headers=headers, timeout=self.request_timeout
+        ) as client:
+            response = await client.post(self.baichuan_api_base, json=payload)
+            response.raise_for_status()
+        return self._create_chat_result(response.json())
+
+    async def _astream(
+        self,
+        messages: List[BaseMessage],
+        stop: Optional[List[str]] = None,
+        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
+        **kwargs: Any,
+    ) -> AsyncIterator[ChatGenerationChunk]:
+        headers = self._create_headers_parameters(**kwargs)
+        payload = self._create_payload_parameters(messages, stream=True, **kwargs)
+        import httpx
+
+        async with httpx.AsyncClient(
+            headers=headers, timeout=self.request_timeout
+        ) as client:
+            async with aconnect_httpx_sse(
+                client, "POST", self.baichuan_api_base, json=payload
+            ) as event_source:
+                async for sse in event_source.aiter_sse():
+                    chunk = json.loads(sse.data)
+                    if len(chunk["choices"]) == 0:
+                        continue
+                    choice = chunk["choices"][0]
+                    chunk = _convert_delta_to_message_chunk(
+                        choice["delta"], AIMessageChunk
+                    )
+                    finish_reason = choice.get("finish_reason", None)
+
+                    generation_info = (
+                        {"finish_reason": finish_reason}
+                        if finish_reason is not None
+                        else None
+                    )
+                    chunk = ChatGenerationChunk(
+                        message=chunk, generation_info=generation_info
+                    )
+                    if run_manager:
+                        await run_manager.on_llm_new_token(chunk.text, chunk=chunk)
+                    yield chunk
+                    if finish_reason is not None:
+                        break
+
+    def _chat(self, messages: List[BaseMessage], **kwargs: Any) -> requests.Response:
+        payload = self._create_payload_parameters(messages, **kwargs)
+        url = self.baichuan_api_base
+        headers = self._create_headers_parameters(**kwargs)
+
+        res = requests.post(
+            url=url,
+            timeout=self.request_timeout,
+            headers=headers,
+            json=payload,
+            stream=self.streaming,
+        )
+        return res
+
+    def _create_payload_parameters(  # type: ignore[no-untyped-def]
+        self, messages: List[BaseMessage], **kwargs
+    ) -> Dict[str, Any]:
+        parameters = {**self._default_params, **kwargs}
         temperature = parameters.pop("temperature", 0.3)
         top_k = parameters.pop("top_k", 5)
         top_p = parameters.pop("top_p", 0.85)
+        model = parameters.pop("model")
         with_search_enhance = parameters.pop("with_search_enhance", False)
         stream = parameters.pop("stream", False)
 
@@ -242,24 +350,21 @@ class ChatBaichuan(BaseChatModel):
             "with_search_enhance": with_search_enhance,
             "stream": stream,
         }
+        return payload
 
-        url = self.baichuan_api_base
+    def _create_headers_parameters(self, **kwargs) -> Dict[str, Any]:  # type: ignore[no-untyped-def]
+        parameters = {**self._default_params, **kwargs}
+        default_headers = parameters.pop("headers", {})
         api_key = ""
         if self.baichuan_api_key:
             api_key = self.baichuan_api_key.get_secret_value()
 
-        res = requests.post(
-            url=url,
-            timeout=self.request_timeout,
-            headers={
-                "Content-Type": "application/json",
-                "Authorization": f"Bearer {api_key}",
-                **headers,
-            },
-            json=payload,
-            stream=self.streaming,
-        )
-        return res
+        headers = {
+            "Content-Type": "application/json",
+            "Authorization": f"Bearer {api_key}",
+            **default_headers,
+        }
+        return headers
 
     def _create_chat_result(self, response: Mapping[str, Any]) -> ChatResult:
         generations = []

libs/community/tests/integration_tests/chat_models/test_baichuan.py

@@ -62,3 +62,17 @@ def test_extra_kwargs() -> None:
     assert chat.temperature == 0.88
     assert chat.top_p == 0.7
     assert chat.with_search_enhance is True
+
+
+async def test_chat_baichuan_agenerate() -> None:
+    chat = ChatBaichuan()  # type: ignore[call-arg]
+    response = await chat.ainvoke("你好呀")
+    assert isinstance(response, AIMessage)
+    assert isinstance(response.content, str)
+
+
+async def test_chat_baichuan_astream() -> None:
+    chat = ChatBaichuan()  # type: ignore[call-arg]
+    async for chunk in chat.astream("今天天气如何？"):
+        assert isinstance(chunk, AIMessage)
+        assert isinstance(chunk.content, str)