code: public function fetch($strTable, $varKey, $strAlias=null)
  	{
  		/** @var Model $strClass */
  		$strClass = Model::getClassFromTable($strTable);
  		$strPk = $strClass::getPk();
  
  		// Search by PK (most common case)
  		if ($strAlias === null || $strAlias == $strPk)
  		{
  			if (isset($this->arrRegistry[$strTable][$varKey]))
  			{
  				return $this->arrRegistry[$strTable][$varKey];
  			}
  
  			return null;
  		}
  
  		// Try to find the model by one of its aliases
  		return $this->fetchByAlias($strTable, $strAlias, $varKey);
  	}
docs: Fetch a model by table name and primary key
  
  @param string $strTable The table name
  @param mixed  $varKey   The key
  @param string $strAlias An optional alias
  
  @return Model|null The model or null