%pip install llama-index-llms-langchain

from langchain.llms import OpenAI

from llama_index.llms.langchain import LangChainLLM

llm = LangChainLLM(llm=OpenAI())

response_gen = llm.stream_complete("Hi this is")

for delta in response_gen:
    print(delta.delta, end="")

 a test

Hello! Welcome to the test. What would you like to learn about?