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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.export class User {  static users: Map<string, User> = new Map();  age?: number;
  constructor(public name: string) {    if (User.users.has(name)) {      throw new Error(`User ${name} already exists`);    }    User.users.set(name, this);  }
  getAge(): number {    if (!this.age) {      throw new Error("Age unknown");    }    return this.age;  }
  setAge(age: number) {    this.age = age;  }}