This is a VFS adapter for Flysystem. It allows you to mount a virtual filesystem.
composer require thephpleague/flysystem-vfsuse League\Flysystem\Vfs\VfsAdapter;
use League\Flysystem\Filesystem;
use VirtualFileSystem\FileSystem as Vfs;
$adapter = new VfsAdapter(new Vfs);
$filesystem = new Filesystem($adapter);