text: LLMChain(llm=llm, prompt=CONDENSE_QUESTION_PROMPT)doc_chain = load_qa_with_sources_chain(llm, chain_type="map_reduce")chain = ConversationalRetrievalChain(    retriever=vectorstore.as_retriever(),    question_generator=question_generator,    combine_docs_chain=doc_chain,)chat_history = []query = "What did the president say about Ketanji Brown Jackson"result = chain({"question": query, "chat_history": chat_history})result["answer"]    " The president said that he nominated Circuit Court of Appeals Judge Ketanji Brown Jackson, who he described as one of the nation's top legal minds, and that she will continue Justice Breyer's legacy of excellence.\nSOURCES: ../../../state_of_the_union.txt"ConversationalRetrievalChain with streaming to stdoutâ€‹Output from the chain will be streamed to stdout token by token in this example.from langchain.chains.llm import LLMChainfrom langchain.callbacks.streaming_stdout import StreamingStdOutCallbackHandlerfrom langchain.chains.conversational_retrieval.prompts import (    CONDENSE_QUESTION_PROMPT,    QA_PROMPT,)from langchain.chains.question_answering import load_qa_chain# Construct a ConversationalRetrievalChain with a streaming llm for combine docs# and a separate, non-streaming llm for question generationllm = OpenAI(temperature=0, openai_api_key=openai_api_key)streaming_llm = OpenAI(    streaming=True,    callbacks=[StreamingStdOutCallbackHandler()],    temperature=0,    openai_api_key=openai_api_key,)question_generator = LLMChain(llm=llm, prompt=CONDENSE_QUESTION_PROMPT)doc_chain = load_qa_chain(streaming_llm,