我用亚马逊云的Lambda函数,通过langChain调用OpenAI API。我把OPENAI_API_KEY存在了Lambda函数的环境变量里了。神奇的是,在创建new ChatOpenAI()实例的时候没有传入OPENAI_API_KEY,还是可以获取到正确的返回值。这是为什么? ``` language import { ChatOpenAI } from "langchain/chat_models/openai"; import { HumanChatMessage, SystemChatMessage } from "langchain/schema"; export const handler = async (event) => { const chat = new ChatOpenAI({ temperature: 0 }); const response = await chat.call([ new HumanChatMessage( "把大象装冰箱一共分几步?" ), new HumanChatMessage( "为什么?" ), ]); return response; }; ```