如何创建自定义聊天模型类

先决条件

本指南假定您熟悉以下概念

聊天模型

本笔记本介绍了如何创建自定义聊天模型包装器，如果您想使用自己的聊天模型或与 LangChain 中直接支持的包装器不同的包装器，则可以使用它。

在扩展 SimpleChatModel 类后，聊天模型需要实现一些必备事项

一个接受消息列表和调用选项（包括stop 序列等）并返回字符串的_call 方法。
一个返回字符串的_llmType 方法。仅用于记录目的。

您还可以实现以下可选方法

一个返回AsyncGenerator 并生成 ChatGenerationChunks 的_streamResponseChunks 方法。这使得 LLM 可以支持流式传输输出。

让我们实现一个非常简单的自定义聊天模型，它只回显输入的前n 个字符。

import {
  SimpleChatModel,
  type BaseChatModelParams,
} from "@langchain/core/language_models/chat_models";
import { CallbackManagerForLLMRun } from "@langchain/core/callbacks/manager";
import { AIMessageChunk, type BaseMessage } from "@langchain/core/messages";
import { ChatGenerationChunk } from "@langchain/core/outputs";

interface CustomChatModelInput extends BaseChatModelParams {
  n: number;
}

class CustomChatModel extends SimpleChatModel {
  n: number;

  constructor(fields: CustomChatModelInput) {
    super(fields);
    this.n = fields.n;
  }

  _llmType() {
    return "custom";
  }

  async _call(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): Promise<string> {
    if (!messages.length) {
      throw new Error("No messages provided.");
    }
    // Pass `runManager?.getChild()` when invoking internal runnables to enable tracing
    // await subRunnable.invoke(params, runManager?.getChild());
    if (typeof messages[0].content !== "string") {
      throw new Error("Multimodal messages are not supported.");
    }
    return messages[0].content.slice(0, this.n);
  }

  async *_streamResponseChunks(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): AsyncGenerator<ChatGenerationChunk> {
    if (!messages.length) {
      throw new Error("No messages provided.");
    }
    if (typeof messages[0].content !== "string") {
      throw new Error("Multimodal messages are not supported.");
    }
    // Pass `runManager?.getChild()` when invoking internal runnables to enable tracing
    // await subRunnable.invoke(params, runManager?.getChild());
    for (const letter of messages[0].content.slice(0, this.n)) {
      yield new ChatGenerationChunk({
        message: new AIMessageChunk({
          content: letter,
        }),
        text: letter,
      });
      // Trigger the appropriate callback for new chunks
      await runManager?.handleLLMNewToken(letter);
    }
  }
}

现在，我们可以像使用任何其他聊天模型一样使用它

const chatModel = new CustomChatModel({ n: 4 });

await chatModel.invoke([["human", "I am an LLM"]]);

AIMessage {
  lc_serializable: true,
  lc_kwargs: {
    content: 'I am',
    tool_calls: [],
    invalid_tool_calls: [],
    additional_kwargs: {},
    response_metadata: {}
  },
  lc_namespace: [ 'langchain_core', 'messages' ],
  content: 'I am',
  name: undefined,
  additional_kwargs: {},
  response_metadata: {},
  id: undefined,
  tool_calls: [],
  invalid_tool_calls: [],
  usage_metadata: undefined
}

并支持流式传输

const stream = await chatModel.stream([["human", "I am an LLM"]]);

for await (const chunk of stream) {
  console.log(chunk);
}

AIMessageChunk {
  lc_serializable: true,
  lc_kwargs: {
    content: 'I',
    tool_calls: [],
    invalid_tool_calls: [],
    tool_call_chunks: [],
    additional_kwargs: {},
    response_metadata: {}
  },
  lc_namespace: [ 'langchain_core', 'messages' ],
  content: 'I',
  name: undefined,
  additional_kwargs: {},
  response_metadata: {},
  id: undefined,
  tool_calls: [],
  invalid_tool_calls: [],
  tool_call_chunks: [],
  usage_metadata: undefined
}
AIMessageChunk {
  lc_serializable: true,
  lc_kwargs: {
    content: ' ',
    tool_calls: [],
    invalid_tool_calls: [],
    tool_call_chunks: [],
    additional_kwargs: {},
    response_metadata: {}
  },
  lc_namespace: [ 'langchain_core', 'messages' ],
  content: ' ',
  name: undefined,
  additional_kwargs: {},
  response_metadata: {},
  id: undefined,
  tool_calls: [],
  invalid_tool_calls: [],
  tool_call_chunks: [],
  usage_metadata: undefined
}
AIMessageChunk {
  lc_serializable: true,
  lc_kwargs: {
    content: 'a',
    tool_calls: [],
    invalid_tool_calls: [],
    tool_call_chunks: [],
    additional_kwargs: {},
    response_metadata: {}
  },
  lc_namespace: [ 'langchain_core', 'messages' ],
  content: 'a',
  name: undefined,
  additional_kwargs: {},
  response_metadata: {},
  id: undefined,
  tool_calls: [],
  invalid_tool_calls: [],
  tool_call_chunks: [],
  usage_metadata: undefined
}
AIMessageChunk {
  lc_serializable: true,
  lc_kwargs: {
    content: 'm',
    tool_calls: [],
    invalid_tool_calls: [],
    tool_call_chunks: [],
    additional_kwargs: {},
    response_metadata: {}
  },
  lc_namespace: [ 'langchain_core', 'messages' ],
  content: 'm',
  name: undefined,
  additional_kwargs: {},
  response_metadata: {},
  id: undefined,
  tool_calls: [],
  invalid_tool_calls: [],
  tool_call_chunks: [],
  usage_metadata: undefined
}

如果您想利用 LangChain 的回调系统来实现令牌跟踪等功能，您可以扩展 BaseChatModel 类并实现更低级的_generate 方法。它也接受BaseMessage 列表作为输入，但要求您构建并返回一个ChatGeneration 对象，该对象允许额外的元数据。以下是一个示例

import { AIMessage, BaseMessage } from "@langchain/core/messages";
import { ChatResult } from "@langchain/core/outputs";
import {
  BaseChatModel,
  BaseChatModelCallOptions,
  BaseChatModelParams,
} from "@langchain/core/language_models/chat_models";
import { CallbackManagerForLLMRun } from "@langchain/core/callbacks/manager";

interface AdvancedCustomChatModelOptions extends BaseChatModelCallOptions {}

interface AdvancedCustomChatModelParams extends BaseChatModelParams {
  n: number;
}

class AdvancedCustomChatModel extends BaseChatModel<AdvancedCustomChatModelOptions> {
  n: number;

  static lc_name(): string {
    return "AdvancedCustomChatModel";
  }

  constructor(fields: AdvancedCustomChatModelParams) {
    super(fields);
    this.n = fields.n;
  }

  async _generate(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): Promise<ChatResult> {
    if (!messages.length) {
      throw new Error("No messages provided.");
    }
    if (typeof messages[0].content !== "string") {
      throw new Error("Multimodal messages are not supported.");
    }
    // Pass `runManager?.getChild()` when invoking internal runnables to enable tracing
    // await subRunnable.invoke(params, runManager?.getChild());
    const content = messages[0].content.slice(0, this.n);
    const tokenUsage = {
      usedTokens: this.n,
    };
    return {
      generations: [{ message: new AIMessage({ content }), text: content }],
      llmOutput: { tokenUsage },
    };
  }

  _llmType(): string {
    return "advanced_custom_chat_model";
  }
}

这将通过回调事件和`streamEvents 方法传递返回的额外信息

const chatModel = new AdvancedCustomChatModel({ n: 4 });

const eventStream = await chatModel.streamEvents([["human", "I am an LLM"]], {
  version: "v2",
});

for await (const event of eventStream) {
  if (event.event === "on_chat_model_end") {
    console.log(JSON.stringify(event, null, 2));
  }
}

{
  "event": "on_chat_model_end",
  "data": {
    "output": {
      "lc": 1,
      "type": "constructor",
      "id": [
        "langchain_core",
        "messages",
        "AIMessage"
      ],
      "kwargs": {
        "content": "I am",
        "tool_calls": [],
        "invalid_tool_calls": [],
        "additional_kwargs": {},
        "response_metadata": {
          "tokenUsage": {
            "usedTokens": 4
          }
        }
      }
    }
  },
  "run_id": "11dbdef6-1b91-407e-a497-1a1ce2974788",
  "name": "AdvancedCustomChatModel",
  "tags": [],
  "metadata": {
    "ls_model_type": "chat"
  }
}

跟踪（高级）

如果您正在实现自定义聊天模型并想将其与 LangSmith 等跟踪服务一起使用，您可以通过在模型上实现invocationParams() 方法来自动记录用于特定调用的参数。

此方法完全可选，但它返回的任何内容都将作为元数据记录到跟踪中。

以下是一种可能使用的模式

import { CallbackManagerForLLMRun } from "@langchain/core/callbacks/manager";
import {
  BaseChatModel,
  type BaseChatModelCallOptions,
  type BaseChatModelParams,
} from "@langchain/core/language_models/chat_models";
import { BaseMessage } from "@langchain/core/messages";
import { ChatResult } from "@langchain/core/outputs";

interface CustomChatModelOptions extends BaseChatModelCallOptions {
  // Some required or optional inner args
  tools: Record<string, any>[];
}

interface CustomChatModelParams extends BaseChatModelParams {
  temperature: number;
  n: number;
}

class CustomChatModel extends BaseChatModel<CustomChatModelOptions> {
  temperature: number;

  n: number;

  static lc_name(): string {
    return "CustomChatModel";
  }

  constructor(fields: CustomChatModelParams) {
    super(fields);
    this.temperature = fields.temperature;
    this.n = fields.n;
  }

  // Anything returned in this method will be logged as metadata in the trace.
  // It is common to pass it any options used to invoke the function.
  invocationParams(options?: this["ParsedCallOptions"]) {
    return {
      tools: options?.tools,
      n: this.n,
    };
  }

  async _generate(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): Promise<ChatResult> {
    if (!messages.length) {
      throw new Error("No messages provided.");
    }
    if (typeof messages[0].content !== "string") {
      throw new Error("Multimodal messages are not supported.");
    }
    const additionalParams = this.invocationParams(options);
    const content = await someAPIRequest(messages, additionalParams);
    return {
      generations: [{ message: new AIMessage({ content }), text: content }],
      llmOutput: {},
    };
  }

  _llmType(): string {
    return "advanced_custom_chat_model";
  }
}

如何创建自定义聊天模型类

跟踪（高级）

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如何创建自定义聊天模型类

跟踪（高级）​

此页面有帮助吗？

您也可以留下详细的反馈 在 GitHub 上.

跟踪（高级）

您也可以留下详细的反馈在 GitHub 上.