text: import { TodoItemModel } from "./TodoItemModel";
  const item = new TodoItemModel({
      title: "未完了のTodoアイテム",
      completed: false
  });
  const completedItem = new TodoItemModel({
      title: "完了済みのTodoアイテム",
      completed: true
  });
  // それぞれの`id`は異なる
  console.log(item.id !== completedItem.id); // => true
  