[openai/openai-cookbook]添加 liteLLM 示例 - 使用 chatGPT 输入/输出调用 Azure、Anthropic、Llama2、Cohere、50 多个 LLM API

此 PR 添加了使用 liteLLM 的示例笔记本：https ://github.com/BerriAI/litellm/

liteLLM 是一个用于简化调用 OpenAI、Azure、Cohere、Anthropic、Huggingface API 端点的包 TLDR：使用 chatGPT 输入/输出格式调用所有 LLM API

下面是它的使用示例：

from litellm import completion

## set ENV variables
# ENV variables can be set in .env file, too. Example in .env.example
os.environ["OPENAI_API_KEY"] = "openai key"
os.environ["COHERE_API_KEY"] = "cohere key"

messages = [{ "content": "Hello, how are you?","role": "user"}]

# openai call
response = completion(model="gpt-3.5-turbo", messages=messages)

# llama2 call
model_name = "replicate/llama-2-70b-chat:2c1608e18606fad2812020dc541930f2d0495ce32eee50074220b87300bc16e1"
response = completion(model_name, messages)

# cohere call
response = completion("command-nightly", messages)

# anthropic call
response = completion(model="claude-instant-1", messages=messages)