langchain-localai is a 3rd party integration package for LocalAI. It provides a simple way to use LocalAI services in LangChain.The source code is available on GitHubLocalAIRerank class. In order to use the LocalAIRerank class, you need to have the LocalAI service hosted somewhere and configure the reranker. See the documentation at localai.io/basics/getting_started/index.html and localai.io/features/reranker/index.html.