text: from django.db import models
  
  
  class Source(models.Model):
      name = models.CharField(unique=True, max_length=255)
  
  
  class ThumbnailMeta(models.Model):
      source = models.ForeignKey(Source, related_name='thumbnails')
      size = models.CharField(max_length=64)
      name = models.CharField(unique=True, max_length=255)
  
      class Meta:
          unique_together = ('source', 'size')
  