private function buildCompleteHeader(): string
    {
        $header = "";
        foreach ($this->headers as $sourceType => $value) {
            $header .= $this->buildHeaderLine($sourceType, $value);
        }
        if (!empty($this->reportUri)) {
            $header .= 'report-uri ' . $this->reportUri . ';';
        }
        return $header;
    }