core-bundle/src/Resources/contao/models/FilesModel.php
public static function findByPk($varValue, array $arrOptions=array())
	{
		if (static::$strPk == 'id')
		{
			return static::findById($varValue, $arrOptions);
		}

		return parent::findByPk($varValue, $arrOptions);
	}
public static function findByPk($varValue, array $arrOptions=array())
	{
		if (static::$strPk == 'id')
		{
			return static::findById($varValue, $arrOptions);
		}

		return parent::findByPk($varValue, $arrOptions);
	}
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