eZ\Publish\Core\Repository\ContentTypeService::unassignContentTypeGroup PHP Method

    public function unassignContentTypeGroup(APIContentType $contentType, APIContentTypeGroup $contentTypeGroup)
    {
        if ($this->repository->hasAccess('class', 'update') !== true) {
            throw new UnauthorizedException('ContentType', 'update');
        }
        $spiContentType = $this->contentTypeHandler->load($contentType->id, $contentType->status);
        if (!in_array($contentTypeGroup->id, $spiContentType->groupIds)) {
            throw new InvalidArgumentException('$contentTypeGroup', 'The given ContentType is not assigned the ContentTypeGroup');
        }
        $this->repository->beginTransaction();
        try {
            $this->contentTypeHandler->unlink($contentTypeGroup->id, $contentType->id, $contentType->status);
            $this->repository->commit();
        } catch (APIBadStateException $e) {
            $this->repository->rollback();
            throw new BadStateException('$contentType', 'The given ContentTypeGroup is the last group assigned to the ContentType', $e);
        } catch (Exception $e) {
            $this->repository->rollback();
            throw $e;
        }
    }