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cypher.ts
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cypher.ts
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import type { BaseLanguageModelInterface } from "@langchain/core/language_models/base";
import { ChainValues } from "@langchain/core/utils/types";
import { BasePromptTemplate } from "@langchain/core/prompts";
import { CallbackManagerForChainRun } from "@langchain/core/callbacks/manager";
import { Neo4jGraph } from "@langchain/community/graphs/neo4j_graph";
import { LLMChain } from "../../chains/llm_chain.js";
import { BaseChain, ChainInputs } from "../base.js";
import { CYPHER_GENERATION_PROMPT, CYPHER_QA_PROMPT } from "./prompts.js";
export const INTERMEDIATE_STEPS_KEY = "intermediateSteps";
export interface GraphCypherQAChainInput extends ChainInputs {
graph: Neo4jGraph;
cypherGenerationChain: LLMChain;
qaChain: LLMChain;
inputKey?: string;
outputKey?: string;
topK?: number;
returnIntermediateSteps?: boolean;
returnDirect?: boolean;
}
export interface FromLLMInput {
graph: Neo4jGraph;
llm?: BaseLanguageModelInterface;
cypherLLM?: BaseLanguageModelInterface;
qaLLM?: BaseLanguageModelInterface;
qaPrompt?: BasePromptTemplate;
cypherPrompt?: BasePromptTemplate;
returnIntermediateSteps?: boolean;
returnDirect?: boolean;
}
/**
* @example
* ```typescript
* const chain = new GraphCypherQAChain({
* llm: new ChatOpenAI({ temperature: 0 }),
* graph: new Neo4jGraph(),
* });
* const res = await chain.run("Who played in Pulp Fiction?");
* ```
*/
export class GraphCypherQAChain extends BaseChain {
private graph: Neo4jGraph;
private cypherGenerationChain: LLMChain;
private qaChain: LLMChain;
private inputKey = "query";
private outputKey = "result";
private topK = 10;
private returnDirect = false;
private returnIntermediateSteps = false;
constructor(props: GraphCypherQAChainInput) {
super(props);
const {
graph,
cypherGenerationChain,
qaChain,
inputKey,
outputKey,
topK,
returnIntermediateSteps,
returnDirect,
} = props;
this.graph = graph;
this.cypherGenerationChain = cypherGenerationChain;
this.qaChain = qaChain;
if (inputKey) {
this.inputKey = inputKey;
}
if (outputKey) {
this.outputKey = outputKey;
}
if (topK) {
this.topK = topK;
}
if (returnIntermediateSteps) {
this.returnIntermediateSteps = returnIntermediateSteps;
}
if (returnDirect) {
this.returnDirect = returnDirect;
}
}
_chainType() {
return "graph_cypher_chain" as const;
}
get inputKeys(): string[] {
return [this.inputKey];
}
get outputKeys(): string[] {
return [this.outputKey];
}
static fromLLM(props: FromLLMInput): GraphCypherQAChain {
const {
graph,
qaPrompt = CYPHER_QA_PROMPT,
cypherPrompt = CYPHER_GENERATION_PROMPT,
llm,
cypherLLM,
qaLLM,
returnIntermediateSteps = false,
returnDirect = false,
} = props;
if (!cypherLLM && !llm) {
throw new Error(
"Either 'llm' or 'cypherLLM' parameters must be provided"
);
}
if (!qaLLM && !llm) {
throw new Error("Either 'llm' or 'qaLLM' parameters must be provided");
}
if (cypherLLM && qaLLM && llm) {
throw new Error(
"You can specify up to two of 'cypherLLM', 'qaLLM', and 'llm', but not all three simultaneously."
);
}
const qaChain = new LLMChain({
llm: (qaLLM || llm) as BaseLanguageModelInterface,
prompt: qaPrompt,
});
const cypherGenerationChain = new LLMChain({
llm: (cypherLLM || llm) as BaseLanguageModelInterface,
prompt: cypherPrompt,
});
return new GraphCypherQAChain({
cypherGenerationChain,
qaChain,
graph,
returnIntermediateSteps,
returnDirect,
});
}
private extractCypher(text: string): string {
const pattern = /```(.*?)```/s;
const matches = text.match(pattern);
return matches ? matches[1] : text;
}
async _call(
values: ChainValues,
runManager?: CallbackManagerForChainRun
): Promise<ChainValues> {
const callbacks = runManager?.getChild();
const question = values[this.inputKey];
const intermediateSteps = [];
const generatedCypher = await this.cypherGenerationChain.call(
{ question, schema: this.graph.getSchema() },
callbacks
);
const extractedCypher = this.extractCypher(generatedCypher.text);
await runManager?.handleText(`Generated Cypher:\n`);
await runManager?.handleText(`${extractedCypher} green\n`);
intermediateSteps.push({ query: extractedCypher });
let chainResult: ChainValues;
const context = await this.graph.query(extractedCypher, {
topK: this.topK,
});
if (this.returnDirect) {
chainResult = { [this.outputKey]: context };
} else {
await runManager?.handleText("Full Context:\n");
await runManager?.handleText(`${context} green\n`);
intermediateSteps.push({ context });
const result = await this.qaChain.call(
{ question, context: JSON.stringify(context) },
callbacks
);
chainResult = {
[this.outputKey]: result[this.qaChain.outputKey],
};
}
if (this.returnIntermediateSteps) {
chainResult[INTERMEDIATE_STEPS_KEY] = intermediateSteps;
}
return chainResult;
}
}