public function allFilters()
    {
        $filters = [];
        foreach ($this->extensions() as $ext) {
            if (empty($this->_data[$ext][self::FILTERS])) {
                continue;
            }
            $filters = array_merge($filters, $this->_data[$ext][self::FILTERS]);
        }
        foreach ($this->_targets as $target) {
            if (empty($target[self::FILTERS])) {
                continue;
            }
            $filters = array_merge($filters, $target[self::FILTERS]);
        }
        return array_unique($filters);
    }