old_contents: import os
  
  from sorl.thumbnail import get_thumbnail
  
  from ajaxuploader.backends.local import LocalUploadBackend
  
  class ThumbnailUploadBackend(LocalUploadBackend):
      def __init__(self, dimension):
          self._dimension = dimension
      
      def upload_complete(self, request, filename):
          thumbnail = get_thumbnail(self._filename, self._dimension)
          os.unlink(self._filename)
          return {"path": thumbnail.name}
  
new_contents: import os
  
  from django.conf import settings
  from sorl.thumbnail import get_thumbnail
  
  from ajaxuploader.backends.local import LocalUploadBackend
  
  class ThumbnailUploadBackend(LocalUploadBackend):
      DIMENSION = "100x100"
  
      def upload_complete(self, request, filename):
          thumbnail = get_thumbnail(self._path, self.DIMENSION)
          os.unlink(self._path)
          return {"path": settings.MEDIA_URL + thumbnail.name}
  
subject: Use dimension as a constant, so we keep same interface for all backends; also returns full path to the place where image was saved