langchain/langchain/retrievers/__init__.py

from langchain.retrievers.chatgpt_plugin_retriever import ChatGPTPluginRetriever
from langchain.retrievers.metal import MetalRetriever
from langchain.retrievers.remote_retriever import RemoteLangChainRetriever

__all__ = ["ChatGPTPluginRetriever", "RemoteLangChainRetriever", "MetalRetriever"]