public function findOtherContentPartFor(Message $message, $mimeType)
    {
        $altPart = $message->getPart(
            0,
            PartFilter::fromInlineContentType(($mimeType === 'text/plain') ? 'text/html' : 'text/plain')
        );
        if ($altPart !== null && $altPart->getParent() !== null && $altPart->getParent()->isMultiPart()) {
            $altPartParent = $altPart->getParent();
            if ($altPartParent->getChildCount(PartFilter::fromDisposition('inline', PartFilter::FILTER_EXCLUDE)) !== 1) {
                $altPart = $this->createMultipartRelatedPartForInlineChildrenOf($altPartParent);
            }
        }
        return $altPart;
    }