Phalcon 4.0 Phalcon\Filter\FilterLocatorFactory();

Recently installed Phalcon 4.0 on a new server and I am refactoring the code to take account of the new changes.

I cannot access the class FilterLocatorFactory(); for some reason.

In the app I have tried use Phalcon\Di; use Phalcon\Filter\FilterLocatorFactory;

$container = new Di();

$container->set(
'filter',
function () {
    $someFilter = new FilterLocatorFactory();
    return $factory->newInstance();
}
);

But this come back with the error:

PHP Fatal error:  Uncaught Error: Class 'Phalcon\\Filter\\FilterLocatorFactory' not found in /var/foo/bar

For maintainability I want to instantiate the filter in the $di then just call it from anywhere using:

$this->filter("mynaastystring","string");

Any advice would be much appreciated. Cannot seem to acces it in on-construct() or inisitalize() either.

Thanks