feat: add ERNIE-Bot-4 Function Calling
Labels: name: auto:enhancement, name: area: models

- **Description:** ERNIE-Bot-Chat-4 Large Language Model adds the ability of `Function Calling` by passing parameters through the `functions` parameter in the request. To simplify function calling for ERNIE-Bot-Chat-4, the `create_ernie_fn_chain()` function has been added. The definition and usage of the `create_ernie_fn_chain()` function is similar to that of the `create_openai_fn_chain()` function.

Examples as the follows:

```
import json

from langchain.chains.ernie_functions import (
    create_ernie_fn_chain,
)
from langchain.chat_models import ErnieBotChat
from langchain.prompts import ChatPromptTemplate

def get_current_news(location: str) -> str:
    """Get the current news based on the location.'

    Args:
        location (str): The location to query.
    
    Returs:
        str: Current news based on the location.
    """

    news_info = {
        "location": location,
        "news": [
            "I have a Book.",
            "It's a nice day, today."
        ]
    }

    return json.dumps(news_info)

def get_current_weather(location: str, unit: str="celsius") -> str:
    """Get the current weather in a given location

    Args:
        location (str): location of the weather.
        unit (str): unit of the tempuature.
    
    Returns:
        str: weather in the given location.
    """

    weather_info = {
        "location": location,
        "temperature": "27",
        "unit": unit,
        "forecast": ["sunny", "windy"],
    }
    return json.dumps(weather_info)

llm = ErnieBotChat(model_name="ERNIE-Bot-4")
prompt = ChatPromptTemplate.from_messages(
    [
        ("human", "{query}"),
    ]
)

chain = create_ernie_fn_chain([get_current_weather, get_current_news], llm, prompt, verbose=True)
res = chain.run("北京今天的新闻是什么？")
print(res)
```

The running results of the above program are shown below：
```
> Entering new LLMChain chain...
Prompt after formatting:
Human: 北京今天的新闻是什么？



> Finished chain.
{'name': 'get_current_news', 'thoughts': '用户想要知道北京今天的新闻。我可以使用get_current_news工具来获取这些信息。', 'arguments': {'location': '北京'}}
```

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