protected function getHeaderSetAdditions($setSpec)
    {
        $insert = '';
        foreach ($setSpec as $current) {
            $set = (string)$current;
            if ($this->injectSetSpec) {
                $insert .= $this->createTag($this->injectSetSpec, $set);
            }
            if ($this->injectSetName) {
                $name = $this->setNames[$set] ?? $set;
                $insert .= $this->createTag($this->injectSetName, $name);
            }
        }
        return $insert;
    }