public function sort(array $sorts = array())
    {
        if (func_num_args() === 0) {
            return $this->sorts;
        }

        $this->sorts = array();

        foreach ($sorts as $key => $value) {
            if ($key[0] === '$') {
                $key[0] = '_';
            }

            $this->sorts[$key] = $value;
        }

        return $this;
    }