public function unlinkContentTypeFromGroup($contentTypeId, $contentTypeGroupId)
    {
        $contentType = $this->contentTypeService->loadContentType($contentTypeId);
        $contentTypeGroup = $this->contentTypeService->loadContentTypeGroup($contentTypeGroupId);

        $existingContentTypeGroups = $contentType->getContentTypeGroups();
        $contentTypeInGroup = false;
        foreach ($existingContentTypeGroups as $existingGroup) {
            if ($existingGroup->id == $contentTypeGroup->id) {
                $contentTypeInGroup = true;
                break;
            }
        }

        if (!$contentTypeInGroup) {
            throw new Exceptions\NotFoundException('Content type is not in the given group');
        }

        if (count($existingContentTypeGroups) == 1) {
            throw new ForbiddenException('Content type cannot be unlinked from the only remaining group');
        }

        $this->contentTypeService->unassignContentTypeGroup(
            $contentType,
            $contentTypeGroup
        );

        $contentType = $this->contentTypeService->loadContentType($contentTypeId);

        return new Values\ContentTypeGroupRefList(
            $contentType,
            $contentType->getContentTypeGroups()
        );
    }