code: public static function findByPk($varValue, array $arrOptions=array())
  	{
  		if (static::$strPk == 'id')
  		{
  			return static::findById($varValue, $arrOptions);
  		}
  
  		return parent::findByPk($varValue, $arrOptions);
  	}
docs: Find a file by its primary key
  
  @param mixed $varValue   The value
  @param array $arrOptions An optional options array
  
  @return FilesModel|Model|null The model or null if there is no file