wp-includes/SimplePie/src/Enclosure.php:620Get the medium
string|null public function get_medium() { if ($this->medium !== null) { return $this->medium; } return null; }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/SimplePie/src/Enclosure.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.