PHPStan does not yet narrow down the return type based on the argument of SimpleXMLElement::saveXML(). Is this something that should be added to PHPStan itself in some function map or so? If so, where would that be? A stub I assume? Mostly asking because I never did this and want to avoid over-complicating it :)

Example https://phpstan.org/r/cbf744fa-0c8d-4fb2-9838-8f7d02199f42