documentation/framework_2_validator_2_file_2_extension_8php_source.html

 <?php
 namespace Magento\Framework\Validator\File;

 class Extension extends \Zend_Validate_File_Extension implements \Magento\Framework\Validator\ValidatorInterface
 {
 }
Magento\Framework\Validator\File\Extension
Definition: Extension.php:10

Magento\Framework\Validator\File
Definition: Extension.php:8

Zend_Validate_File_Extension
Definition: Extension.php:35