community[minor]: integrate chat models with Yuan2.0 (#16575)

1. integrate chat models with
[`Yuan2.0`](https://github.com/IEIT-Yuan/Yuan-2.0/blob/main/README-EN.md)
2. add a new doc for [Yuan2.0
integration](docs/docs/integrations/llms/yuan2.ipynb)
 
Yuan2.0 is a new generation Fundamental Large Language Model developed
by IEIT System. We have published all three models, Yuan 2.0-102B, Yuan
2.0-51B, and Yuan 2.0-2B.

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/tests/integration_tests/chat_models/test_yuan2.py

@@ -0,0 +1,152 @@
+"""Test ChatYuan2 wrapper."""
+from typing import List
+
+import pytest
+from langchain_core.callbacks import CallbackManager
+from langchain_core.messages import BaseMessage, HumanMessage, SystemMessage
+from langchain_core.outputs import (
+    ChatGeneration,
+    LLMResult,
+)
+
+from langchain_community.chat_models.yuan2 import ChatYuan2
+from tests.unit_tests.callbacks.fake_callback_handler import FakeCallbackHandler
+
+
+@pytest.mark.scheduled
+def test_chat_yuan2() -> None:
+    """Test ChatYuan2 wrapper."""
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=False,
+    )
+    messages = [
+        HumanMessage(content="Hello"),
+    ]
+    response = chat(messages)
+    assert isinstance(response, BaseMessage)
+    assert isinstance(response.content, str)
+
+
+def test_chat_yuan2_system_message() -> None:
+    """Test ChatYuan2 wrapper with system message."""
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=False,
+    )
+    messages = [
+        SystemMessage(content="You are an AI assistant."),
+        HumanMessage(content="Hello"),
+    ]
+    response = chat(messages)
+    assert isinstance(response, BaseMessage)
+    assert isinstance(response.content, str)
+
+
+@pytest.mark.scheduled
+def test_chat_yuan2_generate() -> None:
+    """Test ChatYuan2 wrapper with generate."""
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=False,
+    )
+    messages: List = [
+        HumanMessage(content="Hello"),
+    ]
+    response = chat.generate([messages])
+    assert isinstance(response, LLMResult)
+    assert len(response.generations) == 1
+    assert response.llm_output
+    generation = response.generations[0]
+    for gen in generation:
+        assert isinstance(gen, ChatGeneration)
+        assert isinstance(gen.text, str)
+        assert gen.text == gen.message.content
+
+
+@pytest.mark.scheduled
+def test_chat_yuan2_streaming() -> None:
+    """Test that streaming correctly invokes on_llm_new_token callback."""
+    callback_handler = FakeCallbackHandler()
+    callback_manager = CallbackManager([callback_handler])
+
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=True,
+        callback_manager=callback_manager,
+    )
+    messages = [
+        HumanMessage(content="Hello"),
+    ]
+    response = chat(messages)
+    assert callback_handler.llm_streams > 0
+    assert isinstance(response, BaseMessage)
+
+
+@pytest.mark.asyncio
+async def test_async_chat_yuan2() -> None:
+    """Test async generation."""
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=False,
+    )
+    messages: List = [
+        HumanMessage(content="Hello"),
+    ]
+    response = await chat.agenerate([messages])
+    assert isinstance(response, LLMResult)
+    assert len(response.generations) == 1
+    generations = response.generations[0]
+    for generation in generations:
+        assert isinstance(generation, ChatGeneration)
+        assert isinstance(generation.text, str)
+        assert generation.text == generation.message.content
+
+
+@pytest.mark.asyncio
+async def test_async_chat_yuan2_streaming() -> None:
+    """Test that streaming correctly invokes on_llm_new_token callback."""
+    callback_handler = FakeCallbackHandler()
+    callback_manager = CallbackManager([callback_handler])
+
+    chat = ChatYuan2(
+        yuan2_api_key="EMPTY",
+        yuan2_api_base="http://127.0.0.1:8001/v1",
+        temperature=1.0,
+        model_name="yuan2",
+        max_retries=3,
+        streaming=True,
+        callback_manager=callback_manager,
+    )
+    messages: List = [
+        HumanMessage(content="Hello"),
+    ]
+    response = await chat.agenerate([messages])
+    assert callback_handler.llm_streams > 0
+    assert isinstance(response, LLMResult)
+    assert len(response.generations) == 1
+    generations = response.generations[0]
+    for generation in generations:
+        assert isinstance(generation, ChatGeneration)
+        assert isinstance(generation.text, str)
+        assert generation.text == generation.message.content