LangChain QAsRetrievalQAWithSourcesChainBaseCombineDocumentsChain source_documents기본적으로 input으로 들어간 모든 document고 답변에서 관련된 부분은 찾아주지 않음답변과의 연관성 재계산 하지 않는다 Documents | 🦜️🔗 LangchainThese are the core chains for working with documents. They are useful for summarizing documents, answering questions over documents, extracting information from documents, and more.https://python.langchain.com/docs/modules/chains/document/