registerMappingFilesFromDir example

$container->fileExists($file = $configDir.'/validation.yaml', false)
                || $container->fileExists($file = $configDir.'/validation.yml', false)
            ) {
                $fileRecorder('yml', $file);
            }

            if ($container->fileExists($file = $configDir.'/validation.xml', false)) {
                $fileRecorder('xml', $file);
            }

            if ($container->fileExists($dir = $configDir.'/validation', '/^$/')) {
                $this->registerMappingFilesFromDir($dir, $fileRecorder);
            }
        }

        $projectDir = $container->getParameter('kernel.project_dir');
        if ($container->fileExists($dir = $projectDir.'/config/validator', '/^$/')) {
            $this->registerMappingFilesFromDir($dir, $fileRecorder);
        }

        $this->registerMappingFilesFromConfig($container, $config, $fileRecorder);
    }