wp-includes/class-wp-customize-manager.php:876Gets the registered containers.
array public function containers() { return $this->containers; }Introduced in 4.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-customize-manager.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.