code: public function registerAlias(Model $objModel, $strAlias, $varValue)
  	{
  		$strTable = $objModel->getTable();
  		$strPk    = $objModel->getPk();
  		$varPk    = $objModel->$strPk;
  
  		if (isset($this->arrAliases[$strTable][$strAlias][$varValue]))
  		{
  			throw new \RuntimeException("The registry already contains an alias for $strTable::$strPk($varPk) ($strAlias/$varValue)");
  		}
  
  		$this->arrAliases[$strTable][$strAlias][$varValue] = $varPk;
  	}
docs: Register an alias for a model
  
  @param Model  $objModel The model object
  @param string $strAlias The alias name
  @param mixed  $varValue The value of the alias
  
  @throws \RuntimeException If the alias is already registered