/**
  * Permanently deletes the selected rows. When selecting rows for deletion, ignores
  * whether they've been soft-deleted or not. (ie, you don't have to soft-delete objects
  * before you can permanently delete them).
  * Because this will cause a real deletion, related models may block this deletion (ie, add an error
  * and abort the delete)
  * @param array $query_params like EEM_Base::get_all
  * @param boolean $allow_blocking if TRUE, matched objects will only be deleted if there is no related model info
  * that blocks it (ie, there' sno other data that depends on this data); if false, deletes regardless of other objects
  * which may depend on it. Its generally advisable to always leave this as TRUE, otherwise you could easily corrupt your DB
  * @return boolean success
  */
 public function delete_permanently($query_params = array(), $allow_blocking = true)
 {
     $query_params = $this->_alter_query_params_so_deleted_and_undeleted_items_included($query_params);
     return parent::delete_permanently($query_params, $allow_blocking);
 }