Collection.php

<?php
class EM_LayeredNavigation_Model_Resource_Filter_Collection extends Mage_Core_Model_Resource_Db_Collection_Abstract {
    protected function _construct() {
        $this->_init('layerednavigation/filter');
    }

    public function getDisplayConfigs() {
        $this->addFieldToSelect('attribute_code');
        $this->addFieldToSelect('display_as');
        $connection = Mage::getSingleton('core/resource')->getConnection('core_read');
        return $connection->fetchPairs($this->getSelect());
    }
}
?>