Как добавить в поле ManyToManyField?

Question

[sortfact333]

Я создал поле ManyToManyField

class Picture(models.Model):
	link = models.CharField('picture_link', max_length=200)
	def __str__(self):
		return self.link

class MyModel(models.Model):
     picture = models.ManyToManyField(Picture, blank=True)

И пытаюсь добавить модель в поле

for pic in arr:
	_picture = pic.text
	try :
		picture = Picture.objects.get(link = _picture)
	except:
		picture = Picture(link = _picture)
		picture.save()
	mymodel.picture.add(picture)

Но получаю ошибку

Cannot add "<Picture: https://nndd.com/wa-data/public/shop/products/29/13/1329/images/538/538.602x0.jpg>": instance is on database "None", value is on database "default"