54 lines
2.2 KiB
TypeScript
54 lines
2.2 KiB
TypeScript
import type { LanguageModelLike } from "@langchain/core/language_models/base";
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import { type Runnable, type RunnableInterface } from "@langchain/core/runnables";
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import { type BasePromptTemplate } from "@langchain/core/prompts";
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import type { DocumentInterface } from "@langchain/core/documents";
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import type { BaseMessage } from "@langchain/core/messages";
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/**
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* Params for the createHistoryAwareRetriever method.
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*/
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export type CreateHistoryAwareRetrieverParams = {
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/**
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* Language model to use for generating a search term given chat history.
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*/
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llm: LanguageModelLike;
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/**
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* RetrieverLike object that takes a string as input and outputs a list of Documents.
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*/
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retriever: RunnableInterface<string, DocumentInterface[]>;
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/**
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* The prompt used to generate the search query for the retriever.
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*/
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rephrasePrompt: BasePromptTemplate;
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};
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/**
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* Create a chain that takes conversation history and returns documents.
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* If there is no `chat_history`, then the `input` is just passed directly to the
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* retriever. If there is `chat_history`, then the prompt and LLM will be used
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* to generate a search query. That search query is then passed to the retriever.
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* @param {CreateHistoryAwareRetriever} params
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* @returns An LCEL Runnable. The runnable input must take in `input`, and if there
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* is chat history should take it in the form of `chat_history`.
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* The Runnable output is a list of Documents
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* @example
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* ```typescript
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* // yarn add langchain @langchain/openai
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*
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* import { ChatOpenAI } from "@langchain/openai";
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* import { pull } from "langchain/hub";
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* import { createHistoryAwareRetriever } from "langchain/chains/history_aware_retriever";
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*
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* const rephrasePrompt = await pull("langchain-ai/chat-langchain-rephrase");
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* const llm = new ChatOpenAI({});
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* const retriever = ...
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* const chain = await createHistoryAwareRetriever({
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* llm,
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* retriever,
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* rephrasePrompt,
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* });
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* const result = await chain.invoke({"input": "...", "chat_history": [] })
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* ```
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*/
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export declare function createHistoryAwareRetriever({ llm, retriever, rephrasePrompt, }: CreateHistoryAwareRetrieverParams): Promise<Runnable<{
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input: string;
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chat_history: string | BaseMessage[];
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}, DocumentInterface[]>>;
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