private function formListOfDuplicatedBlocks($activeBlockTemplates)
    {
        $templateBlocksToExchange = [];
        $customThemeId = \OxidEsales\Eshop\Core\Registry::getConfig()->getConfigParam('sCustomTheme');

        foreach ($activeBlockTemplates as $activeBlockTemplate) {
            if ($activeBlockTemplate['OXTHEME']) {
                if ($customThemeId && $customThemeId === $activeBlockTemplate['OXTHEME']) {
                    $templateBlocksToExchange['custom_theme'][] = $this->prepareBlockKey($activeBlockTemplate);
                } else {
                    $templateBlocksToExchange['theme'][] = $this->prepareBlockKey($activeBlockTemplate);
                }
            }
        }

        return $templateBlocksToExchange;
    }