public static function fetchObject( $def, $field_filters, $conds, $asObject = true, $grouping = null, $custom_fields = null )
    {
        $rows = eZPersistentObject::fetchObjectList( $def, $field_filters, $conds,
                                                      array(), null, $asObject,
                                                      $grouping, $custom_fields );
        if ( $rows )
            return $rows[0];
        return null;
    }