Add example using Llama2, Palm, Cohere, Replicate Models - using litellm

[ishaan-jaff]

I'm the maintainer of litellm https://github.com/BerriAI/litellm/ - a lightweight package to simplify LLM API calls - Azure, OpenAI, Cohere, Anthropic, Replicate. Manages input/output translation

and was hoping to work on an example on how to make an app using multiple LLMs

Here's how litellm calls work:

from litellm import completion

## set ENV variables
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)

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