public function _unset($name, $emulate = null)
  {
    $name = $this->get_field_name($name);
    $this->_operations['$unset'][$name] = 1;
    if ($emulate === FALSE || ($emulate === null && $this->_emulate === FALSE))
    {
      return $this->_set_dirty($name);
    }
    else
    {
      self::unset_named_reference($this->_object, $name);
      return $this;
    }
  }