DRF, update a single field in nested serializer - django

Question

these are my models:
class ADS(models.Model):
advertiser = models.ForeignKey(User)
campaign = models.ForeignKey(Campaign, related_name="ads")
headline = models.CharField(max_length=50)
description_1 = models.TextField(blank=True)
description_2 = models.TextField(blank=True)
display_url = models.URLField(blank=True)
final_url = models.URLField(blank=True)
mobile_url = models.URLField(blank=True)
class Meta:
db_table = "ads"
and:
class AdsImages(models.Model):
ads = models.ForeignKey(ADS,blank=True, null=True)
image = models.ImageField(upload_to='images/',default='media/None/no-img.jpg')
class Meta:
db_table = "ads_images"
I have a nested serializer, as you can see the second model is a table with images, so I am uploading asynchronously the images via AngularJs. As you can see the ForeignKey(ADS, blank=True, null=True), so I am not filling it for the first time. My question is that how to update after that the ads field.
here are my serializers:
class AdsImagesSerializer(serializers.ModelSerializer):
image = serializers.ImageField(use_url=True,allow_empty_file=True)
class Meta:
model = AdsImages
fields = ('id','image','ads',)
class ADSerializer(serializers.ModelSerializer):
adsImages = AdsImagesSerializer(many=True)
class Meta:
model = ADS
fields = ('headline','description_1','description_2','display_url','final_url','mobile_url','advertiser','adsImages',)

Answer 1

Partial updates
By default, serializers must be passed values for all required fields or they will raise validation errors. You can use the partial argument in order to allow partial updates
# Update `comment` with partial data
serializer = CommentSerializer(comment, data={'content': u'foo bar'}, partial=True)