import { ChatOpenAI } from "@langchain/openai";
import { ChatPromptTemplate } from "@langchain/core/prompts";
const prompt = ChatPromptTemplate.fromTemplate("{x} {y} {z}?").partial({ x: "why is", z: "blue" });
const chain = prompt.pipe(new ChatOpenAI({ model: "gpt-3.5-turbo" }));
const result = await chain.invoke({ y: "sky" });
console.log("Response:", result);