wp-includes/customize/class-wp-customize-themes-section.php:56Gets section parameters for JS.
array public function json() { $exported = parent::json(); $exported['action'] = $this->action; $exported['filter_type'] = $this->filter_type; return $exported; }Introduced in 4.9.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/customize/class-wp-customize-themes-section.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.