如何从Django多对多相关模型生成多项选择域

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField('Author')

class Author(models.Model):
    name = models.CharField(max_length=100)

from django.shortcuts import render
from .models import Author

def book_form(request):
    authors = Author.objects.all()
    return render(request, 'book_form.html', {'authors': authors})

<form method="post">
    {% csrf_token %}
    <label for="title">Book Title:</label>
    <input type="text" id="title" name="title"><br><br>
    <label for="authors">Authors:</label>
    <select multiple id="authors" name="authors">
        {% for author in authors %}
            <option value="{{ author.id }}">{{ author.name }}</option>
        {% endfor %}
    </select><br><br>
    <input type="submit" value="Submit">
</form>