public static function createMultiple($terms, $taxonomy = null)
    {
        if (!Arr::iterable($terms)) {
            return $terms;
        }
        
        $out = array();
        foreach ($terms as $term) {
            $instance = self::create($term, $taxonomy);
            $out[$instance->get('term_id')] = $instance;
        }
        return $out;
    }