protected function _prepareCollection()
    {
        parent::_prepareCollection();
        $collection = $this->getCollection();
        $turpentineEnabled = false;
        $fullPageEnabled = false;
        foreach ($collection as $key=>$item) {
            if ($item->getStatus() == 1 && ($item->getId() == 'turpentine_pages' || $item->getId() == 'turpentine_esi_blocks')) {
                $turpentineEnabled = true;
            }
            if ($item->getStatus() == 1 && $item->getId() == 'full_page') {
                $fullPageEnabled = true;
            }
        }
        if ($turpentineEnabled  && !$fullPageEnabled) {
            $collection->removeItemByKey('full_page');
        }
        if ($fullPageEnabled && !$turpentineEnabled) {
            $collection->removeItemByKey('turpentine_pages');
            $collection->removeItemByKey('turpentine_esi_blocks');
        }
        $this->setCollection($collection);
        return $this;
    }