public function getContentType(bool $allowUnverified = false): string
    {
        # always use the verified content type if it exists
        if ($this->contentType === null) {
            if ($allowUnverified) {
                return $this->unverifiedContentType;
            }
            $this->contentType = $this->getContentTypeFromFile($this->tempPath);
        }
        return $this->contentType;
    }