This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.
Plugin::add_customizer()
Implements WP customizer functionality
Source
File: includes/libs/plugin.class.php
private function add_customizer(){
if( is_admin() || is_customize_preview() ) {
$this->customizer = new Customizer();
}
}