无法对mobx-state-tree数组执行forEach

import { types } from "mobx-state-tree";

const Todo = types
  .model({
    id: types.identifier,
    title: types.string,
    completed: false
  })
  .actions(self => ({
    toggle() {
      self.completed = !self.completed;
    }
  }));

const TodoList = types
  .model({
    todos: types.array(Todo)
  })
  .actions(self => ({
    add(todo) {
      self.todos.push(todo);
    }
  }));

const store = TodoList.create({
  todos: []
});

store.add(Todo.create({ id: "1", title: "Buy groceries" }));
store.add(Todo.create({ id: "2", title: "Clean the house" }));

store.todos.forEach(todo => {
  console.log(todo.title);
});