问如何在django-rest-framework中通过关系使用ManytoManyField

EN

class Playlist(models.Model):
    key = models.CharField(max_length=255,blank=True, unique=True)
    user = models.ForeignKey(User)
    title = models.CharField(max_length=200)
    pub_date = models.DateTimeField(auto_now_add=True)
    videos = models.ManyToManyField(Video, through='PlaylistVideo')

class PlaylistVideo(models.Model):
    playlist = models.ForeignKey(Playlist)
    video =    models.ForeignKey(Video)
    position = models.IntegerField()

class Video(models.Model):
    title = models.CharField(max_length=255,blank=True)
    description = models.TextField(blank=True)
    thumb =  models.URLField(blank=True)
    duration = models.IntegerField(default=0)

{
        "key": "h8x3",
        "title": "First Playlist",
        "pub_date": "2012-10-11T17:00:26Z",
        "videos": [
            {
                ....
            },
            {
                ....
            }
        ]
    },