I want to use an open source LLM as a RAG agent that also has memory of the current conversation (and eventually I want to work up to memory of previous conversations). I was looking into conversational retrieval agents from Langchain (linked below), but it seems they only work with OpenAI models. Is it possible to get an open source LLM to work with RAG and conversational memory using Langchain?

https://python.langchain.com/docs/use_cases/question_answering/conversational_retrieval_agents