def set(self, alias, options, target=None):
        """
        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).
        """
        target = self._coerce_target(target) or ''
        target_aliases = self._aliases.setdefault(target, {})
        target_aliases[alias] = options
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).