public function getCollection()
 {
     if (method_exists($this->_collection, 'addFieldToFilter')) {
         foreach ($this->_filters as $field => $condition) {
             $this->_collection->addFieldToFilter($field, $condition);
         }
     } elseif (method_exists($this->_collection, 'addAttributeToFilter')) {
         foreach ($this->_filters as $field => $condition) {
             $this->_collection->addAttributeToFilter($field, $condition);
         }
     }
     return $this->_collection;
 }