public function all($app = NULL) : Bool
    {
        if( ! is_string($app) )
        {
            if( $app === NULL )
            {
                $MLFiles = Filesystem::getFiles($this->appdir, 'ml');
            }
            elseif( is_array($app) )
            {
                $MLFiles = $app;
            }
            else
            {
                return false;
            }

            $allMLFiles = [];

            if( ! empty($MLFiles) ) foreach( $MLFiles as $file )
            {
                $removeExtension = str_replace($this->extension, '', $file);
                $this->all($removeExtension);
            }

            return true;
        }
        else
        {
            $createFile = $this->_langFile($app);
      
            if( is_file($createFile) )
            {
                return unlink($createFile);
            }

            return false;
        }
    }