Outline is an open-source collaborative knowledge base platform designed for team information sharing.

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Setup

You first need to create an api key for your Outline instance. Then you need to set the following environment variables: 
import os

os.environ["OUTLINE_API_KEY"] = "xxx"
os.environ["OUTLINE_INSTANCE_URL"] = "https://app.getoutline.com"

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Retriever

See a usage example. 
from langchain.retrievers import OutlineRetriever