I have been watching this great tutorial : https://www.youtube.com/watch?v=yF9kGESAi3M but am kind of stuck at the execution of the 4_rag/6_rag_one_off_question.py execution. No matter what I do when am embedding all the file in "books" directory the "langchain_demo.txt" file is not getting embedded, cause when a relevant query is asked regarding that, am receiving irrelevant response.