/**
  * This method is called only if $this->delete() was successful. It is
  *   often used for cleaning up other things like custom fields or related
  *   objects.
  *
  * @return \w2p_Core_BaseObject
  */
 protected function hook_postDelete()
 {
     /**
      * @todo I don't like that we have to initialize this null but it's
      *   needed to delete the custom field values from the object we just
      *   deleted.
      */
     $custom_field = new w2p_Core_CustomField('notUsed', 'notUsed2', 'notUsed3', 'notUsed4', 'notUsed5', 'notUsed6');
     $custom_field->deleteByObject($this->_old_key);
     addHistory($this->_tbl, $this->{$this->_tbl_key}, 'delete');
     return $this;
 }