code: def set(self, alias, options, target=None):
          
          target = self._coerce_target(target) or ''
          target_aliases = self._aliases.setdefault(target, {})
          target_aliases[alias] = options
docs: Add an alias.
  
          :param alias: The name of the alias to add.
          :param options: The easy-thumbnails options dictonary for this alias
              (should include ``size``).
          :param target: A field, model, or app to limit this alias to
              (optional).