code: public function unregister(Model $objModel)
  	{
  		$intObjectId = spl_object_hash($objModel);
  
  		// The model is not registered
  		if (!isset($this->arrIdentities[$intObjectId]))
  		{
  			return;
  		}
  
  		$strTable = $objModel->getTable();
  		$strPk    = $objModel->getPk();
  		$intPk    = $objModel->$strPk;
  
  		unset($this->arrIdentities[$intObjectId]);
  		unset($this->arrRegistry[$strTable][$intPk]);
  
  		// Allow the model to modify the registry
  		$objModel->onUnregister($this);
  	}
docs: Unregister a model from the registry
  
  @param Model $objModel The model object