core-bundle/src/Resources/contao/library/Contao/Model/Registry.php
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);
	}
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);
	}
Unregister a model from the registry

@param Model $objModel The model object