TYPO3 Core

In t3lib_file_Repository_FileCollectionRepository the method findByType just calls his parent

/**
 * Finds record collection by type.
 *
 * @param string $type The type to be looked up
 * @return NULL|t3lib_file_Collection_AbstractFileCollection[]
 */
public function findByType($type) {
    return parent::findByType($type);
}

This is quite useless, because due OOP, the parent method (t3lib_collection_RecordCollectionRepository::findByType) is called, if t3lib_file_Repository_FileCollectionRepository does not provide a local / override method.