Why does the Uncaught Error: Class 'Twig_Loader_Filesystem' not found error appear?

Question

Twig

After this code
, the following error appears

Answer 1

In general, Twig has changed something in its logic... I started copy-pasting the code from the old project to the new one and also encountered this error.
It turned out that now you need to connect:

$loader = new \Twig\Loader\FilesystemLoader('...');
$twig = new \Twig\Environment($loader);

Answer 2

Where is the Twig folder? If at the root, then connect it like that?
and you need to insert the code, I'm not an editor to screen