code: public function onUnregister(Registry $registry)
  	{
  		// Unregister aliases to unique fields
  		foreach (static::getUniqueFields() as $strColumn)
  		{
  			$varAliasValue = $this->{$strColumn};
  
  			if ($registry->isRegisteredAlias($this, $strColumn, $varAliasValue))
  			{
  				$registry->unregisterAlias($this, $strColumn, $varAliasValue);
  			}
  		}
  	}
docs: Called when the model is detached from the model registry
  
  @param Registry $registry The model registry