includes(model) {
    return this.models.some((m) => m.toString() === model.toString());
  }
Checks if the Collection includes the given model.

    ```js
    posts.includes(newPost);
    ```

    Works by checking if the given model name and id exists in the Collection,
    making it a bit more flexible than strict object equality.

    ```js
    let post = server.create('post');
    let programming = server.create('tag', { text: 'Programming' });

    visit(`/posts/${post.id}`);
    click('.tag-selector');
    click('.tag:contains(Programming)');

    post.reload();
    assert.ok(post.tags.includes(programming));
    ```

    @method includes
    @return {Boolean}
    @public