private static function get_user_opted_in_module_ids_map( $fs_user_id ) {
            self::$_static_logger->entrance();

            if ( ! is_multisite() ) {
                $installs = array_merge(
                    self::get_all_sites( WP_FS__MODULE_TYPE_PLUGIN ),
                    self::get_all_sites( WP_FS__MODULE_TYPE_THEME )
                );
            } else {
                $sites = self::get_sites();

                $installs = array();
                foreach ( $sites as $site ) {
                    $blog_id = self::get_site_blog_id( $site );

                    $installs = array_merge(
                        $installs,
                        self::get_all_sites( WP_FS__MODULE_TYPE_PLUGIN, $blog_id ),
                        self::get_all_sites( WP_FS__MODULE_TYPE_THEME, $blog_id )
                    );
                }
            }

            $module_ids_map = array();
            foreach ( $installs as $install ) {
                if ( is_object( $install ) &&
                     FS_Site::is_valid_id( $install->id ) &&
                     FS_User::is_valid_id( $install->user_id ) &&
                     ( $install->user_id == $fs_user_id )
                ) {
                    $module_ids_map[ $install->plugin_id ] = true;
                }
            }

            return $module_ids_map;
        }