langchain/libs/community/langchain_community/chains/graph_qa/kuzu.py

"""Question answering over a graph."""
from __future__ import annotations

import re
from typing import Any, Dict, List, Optional

from langchain.chains.base import Chain
from langchain.chains.llm import LLMChain
from langchain_core.callbacks import CallbackManagerForChainRun
from langchain_core.language_models import BaseLanguageModel
from langchain_core.prompts import BasePromptTemplate
from langchain_core.pydantic_v1 import Field

from langchain_community.chains.graph_qa.prompts import (
    CYPHER_QA_PROMPT,
    KUZU_GENERATION_PROMPT,
)
from langchain_community.graphs.kuzu_graph import KuzuGraph


def remove_prefix(text: str, prefix: str) -> str:
    """Remove a prefix from a text.

    Args:
        text: Text to remove the prefix from.
        prefix: Prefix to remove from the text.

    Returns:
        Text with the prefix removed.
    """
    if text.startswith(prefix):
        return text[len(prefix) :]
    return text


def extract_cypher(text: str) -> str:
    """Extract Cypher code from a text.

    Args:
        text: Text to extract Cypher code from.

    Returns:
        Cypher code extracted from the text.
    """
    # The pattern to find Cypher code enclosed in triple backticks
    pattern = r"```(.*?)```"

    # Find all matches in the input text
    matches = re.findall(pattern, text, re.DOTALL)

    return matches[0] if matches else text


class KuzuQAChain(Chain):
    """Question-answering against a graph by generating Cypher statements for Kùzu.

    *Security note*: Make sure that the database connection uses credentials
        that are narrowly-scoped to only include necessary permissions.
        Failure to do so may result in data corruption or loss, since the calling
        code may attempt commands that would result in deletion, mutation
        of data if appropriately prompted or reading sensitive data if such
        data is present in the database.
        The best way to guard against such negative outcomes is to (as appropriate)
        limit the permissions granted to the credentials used with this tool.

        See https://python.langchain.com/docs/security for more information.
    """

    graph: KuzuGraph = Field(exclude=True)
    cypher_generation_chain: LLMChain
    qa_chain: LLMChain
    input_key: str = "query"  #: :meta private:
    output_key: str = "result"  #: :meta private:

    @property
    def input_keys(self) -> List[str]:
        """Return the input keys.

        :meta private:
        """
        return [self.input_key]

    @property
    def output_keys(self) -> List[str]:
        """Return the output keys.

        :meta private:
        """
        _output_keys = [self.output_key]
        return _output_keys

    @classmethod
    def from_llm(
        cls,
        llm: BaseLanguageModel,
        *,
        qa_prompt: BasePromptTemplate = CYPHER_QA_PROMPT,
        cypher_prompt: BasePromptTemplate = KUZU_GENERATION_PROMPT,
        **kwargs: Any,
    ) -> KuzuQAChain:
        """Initialize from LLM."""
        qa_chain = LLMChain(llm=llm, prompt=qa_prompt)
        cypher_generation_chain = LLMChain(llm=llm, prompt=cypher_prompt)

        return cls(
            qa_chain=qa_chain,
            cypher_generation_chain=cypher_generation_chain,
            **kwargs,
        )

    def _call(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        """Generate Cypher statement, use it to look up in db and answer question."""
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        callbacks = _run_manager.get_child()
        question = inputs[self.input_key]

        generated_cypher = self.cypher_generation_chain.run(
            {"question": question, "schema": self.graph.get_schema}, callbacks=callbacks
        )
        # Extract Cypher code if it is wrapped in triple backticks
        # with the language marker "cypher"
        generated_cypher = remove_prefix(extract_cypher(generated_cypher), "cypher")

        _run_manager.on_text("Generated Cypher:", end="\n", verbose=self.verbose)
        _run_manager.on_text(
            generated_cypher, color="green", end="\n", verbose=self.verbose
        )
        context = self.graph.query(generated_cypher)

        _run_manager.on_text("Full Context:", end="\n", verbose=self.verbose)
        _run_manager.on_text(
            str(context), color="green", end="\n", verbose=self.verbose
        )

        result = self.qa_chain(
            {"question": question, "context": context},
            callbacks=callbacks,
        )
        return {self.output_key: result[self.qa_chain.output_key]}