chains.py

from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.embeddings import OllamaEmbeddings, SentenceTransformerEmbeddings
from langchain.chat_models import ChatOpenAI, ChatOllama
from langchain.vectorstores.neo4j_vector import Neo4jVector
from langchain.chains import RetrievalQAWithSourcesChain
from langchain.chains.qa_with_sources import load_qa_with_sources_chain
from langchain.prompts.chat import (
    ChatPromptTemplate,
    SystemMessagePromptTemplate,
    HumanMessagePromptTemplate,
)
from typing import List, Any
from utils import BaseLogger


def load_embedding_model(embedding_model_name: str, logger=BaseLogger(), config={}):
    if embedding_model_name == "ollama":
        embeddings = OllamaEmbeddings(
            base_url=config["ollama_base_url"], model="llama2"
        )
        dimension = 4096
        logger.info("Embedding: Using Ollama")
    elif embedding_model_name == "openai":
        embeddings = OpenAIEmbeddings()
        dimension = 1536
        logger.info("Embedding: Using OpenAI")
    else:
        embeddings = SentenceTransformerEmbeddings(
            model_name="all-MiniLM-L6-v2", cache_folder="/embedding_model"
        )
        dimension = 384
        logger.info("Embedding: Using SentenceTransformer")
    return embeddings, dimension


def load_llm(llm_name: str, logger=BaseLogger(), config={}):
    if llm_name == "gpt-4":
        logger.info("LLM: Using GPT-4")
        return ChatOpenAI(temperature=0, model_name="gpt-4", streaming=True)
    elif llm_name == "gpt-3.5":
        logger.info("LLM: Using GPT-3.5")
        return ChatOpenAI(temperature=0, model_name="gpt-3.5-turbo", streaming=True)
    elif len(llm_name):
        logger.info(f"LLM: Using Ollama: {llm_name}")
        return ChatOllama(
            temperature=0,
            base_url=config["ollama_base_url"],
            model=llm_name,
            streaming=True,
            top_k=10,  # A higher value (100) will give more diverse answers, while a lower value (10) will be more conservative.
            top_p=0.3,  # Higher value (0.95) will lead to more diverse text, while a lower value (0.5) will generate more focused text.
            num_ctx=3072,  # Sets the size of the context window used to generate the next token.
        )
    logger.info("LLM: Using GPT-3.5")
    return ChatOpenAI(temperature=0, model_name="gpt-3.5-turbo", streaming=True)


def configure_llm_only_chain(llm):
    # LLM only response
    template = """
    You are a helpful assistant that helps a support agent with answering programming questions.
    If you don't know the answer, just say that you don't know, don't try to make up an answer.
    """
    system_message_prompt = SystemMessagePromptTemplate.from_template(template)
    human_template = "{text}"
    human_message_prompt = HumanMessagePromptTemplate.from_template(human_template)
    chat_prompt = ChatPromptTemplate.from_messages(
        [system_message_prompt, human_message_prompt]
    )

    def generate_llm_output(
        user_input: str, callbacks: List[Any], prompt=chat_prompt
    ) -> str:
        answer = llm(
            prompt.format_prompt(
                text=user_input,
            ).to_messages(),
            callbacks=callbacks,
        ).content
        return {"answer": answer}

    return generate_llm_output


def configure_qa_rag_chain(llm, embeddings, embeddings_store_url, username, password):
    # RAG response
    general_system_template = """ 
    Use the following pieces of context to answer the question at the end.
    The context contains question-answer pairs and their links from Stackoverflow.
    You should prefer information from accepted or more upvoted answers.
    Make sure to rely on information from the answers and not on questions to provide accuate responses.
    When you find particular answer in the context useful, make sure to cite it in the answer using the link.
    If you don't know the answer, just say that you don't know, don't try to make up an answer.
    ----
    {summaries}
    ----
    Each answer you generate should contain a section at the end of links to 
    Stackoverflow questions and answers you found useful, which are described under Source value.
    You can only use links to StackOverflow questions that are present in the context and always
    add links to the end of the answer in the style of citations.
    Generate concise answers with references sources section of links to 
    relevant StackOverflow questions only at the end of the answer.
    """
    general_user_template = "Question:```{question}```"
    messages = [
        SystemMessagePromptTemplate.from_template(general_system_template),
        HumanMessagePromptTemplate.from_template(general_user_template),
    ]
    qa_prompt = ChatPromptTemplate.from_messages(messages)

    qa_chain = load_qa_with_sources_chain(
        llm,
        chain_type="stuff",
        prompt=qa_prompt,
    )

    # Vector + Knowledge Graph response
    kg = Neo4jVector.from_existing_index(
        embedding=embeddings,
        url=embeddings_store_url,
        username=username,
        password=password,
        database="neo4j",  # neo4j by default
        index_name="stackoverflow",  # vector by default
        text_node_property="body",  # text by default
        retrieval_query="""
    WITH node AS question, score AS similarity
    CALL  { with question
        MATCH (question)<-[:ANSWERS]-(answer)
        WITH answer
        ORDER BY answer.is_accepted DESC, answer.score DESC
        WITH collect(answer)[..2] as answers
        RETURN reduce(str='', answer IN answers | str + 
                '\n### Answer (Accepted: '+ answer.is_accepted +
                ' Score: ' + answer.score+ '): '+  answer.body + '\n') as answerTexts
    } 
    RETURN '##Question: ' + question.title + '\n' + question.body + '\n' 
        + answerTexts AS text, similarity as score, {source: question.link} AS metadata
    ORDER BY similarity ASC // so that best answers are the last
    """,
    )

    kg_qa = RetrievalQAWithSourcesChain(
        combine_documents_chain=qa_chain,
        retriever=kg.as_retriever(search_kwargs={"k": 2}),
        reduce_k_below_max_tokens=False,
        max_tokens_limit=3375,
    )
    return kg_qa