wp-includes/SimplePie/src/File.php:392Sets headers internally.
$headersarray private function set_headers(array $headers): void { $this->parsed_headers = $headers; $this->headers = self::flatten_headers($headers); $this->last_headers = $this->headers; }Unchanged from 6.9.7 through 7.1.0.
Signature, return type and hooks compared across 3 parsed releases.
src/wp-includes/SimplePie/src/File.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.