DjangoRestFramework的外键反向关系序列化的一个问题

class Album(models.Model):
album_name = models.CharField(max_length=100)
artist = models.CharField(max_length=100)

class Track(models.Model):
album = models.ForeignKey(Album, related_name='tracks', on_delete=models.CASCADE)
order = models.IntegerField()
title = models.CharField(max_length=100)
duration = models.IntegerField()

class Meta:
unique_together = ('album', 'order')
ordering = ['order']

def __unicode__(self):
return '%d: %s' % (self.order, self.title)

class TrackSerializer(serializers.ModelSerializer):
class Meta:
model = Track
fields = ('order', 'title', 'duration')

class AlbumSerializer(serializers.ModelSerializer):
tracks = TrackSerializer(many=True, read_only=True)

class Meta:
model = Album
fields = ('album_name', 'artist', 'tracks')

related_name='tracks'