Method getInstance

/**
 * Returns a reference to the global Installer object, only creating it
 * if it doesn't already exist.
 *
 * @return  Updater  An installer object
 *
 * @since   1.7.0
 */
public static function getInstance()
{
    if (!isset(self::$instance)) {
        self::$instance = new static();
    }
    return self::$instance;
}