function get_installed_addons() {
            $installed_addons = array();
            foreach ( self::$_instances as $instance ) {
                if ( $instance->is_addon() && is_object( $instance->_parent_plugin ) ) {
                    if ( $this->_plugin->id == $instance->_parent_plugin->id ) {
                        $installed_addons[] = $instance;
                    }
                }
            }

            return $installed_addons;
        }