ETL

I found this solution: in `query_data.py` I edited the `get_chain` function to include `ConversationalRetrievalChain` instead of `ChatVectorDBChain`, it seems to work with `LangChain==v0.0.139` ```python def get_chain( vectorstore: VectorStore, question_handler, stream_handler,...

> @efraintorlo I turned this into a PR. Hopefully, it will be merged soon. Thanks @pors