bs4 chromadb gradio langchain==0.0.336 langchain_community langchain-openai langchainhub langgraph openai pymongo pypdf numpy python-dotenv tiktoken yt_dlp text_generation transformers sentence-transformers mdtex2html pypinyin socksio tqdm colorama Pygments llama_index markdown markdown2 duckduckgo_search tavily-python scikit-learn nltk pyspellchecker hugchat reportlab PyPDF2