public function addFilters(array $filters)
    {
        foreach ($filters as $key => $filter) {
            $this->addFilter($filter);

            /** Name the expression if $key is a non-numeric string. */
            if (is_string($key) && !is_numeric($key)) {
                $filter = end($this->filters);
                $filter->setName($key);
            }
        }

        return $this;
    }