docs: def serialize_upload(name, storage, url):
      """
      Serialize uploaded file by name and storage. Namespaced by the upload url.
      """
      if isinstance(storage, LazyObject):
          # Unwrap lazy storage class
          storage._setup()
          cls = storage._wrapped.__class__
      else:
          cls = storage.__class__
      return signing.dumps({
          'name': name,
          'storage': '%s.%s' % (cls.__module__, cls.__name__)
      }, salt=url)