private function embed_submenu_items() {
            $item_template = $this->_menu->is_top_level() ?
                '<span class="fs-submenu-item %s %s %s">%s</span>' :
                '<span class="fs-submenu-item fs-sub %s %s %s">%s</span>';

            $top_level_menu_capability = $this->get_top_level_menu_capability();

            ksort( $this->_menu_items );

            $is_first_submenu_item = true;

            foreach ( $this->_menu_items as $priority => $items ) {
                foreach ( $items as $item ) {
                    $capability = ( ! empty( $item['capability'] ) ? $item['capability'] : $top_level_menu_capability );

                    $menu_item = sprintf(
                        $item_template,
                        $this->get_unique_affix(),
                        $item['menu_slug'],
                        ! empty( $item['class'] ) ? $item['class'] : '',
                        $item['menu_title']
                    );

                    $top_level_menu_slug = $this->get_top_level_menu_slug();
                    $menu_slug           = $this->_menu->get_slug( $item['menu_slug'] );

                    if ( ! isset( $item['url'] ) ) {
                        $hook = FS_Admin_Menu_Manager::add_subpage(
                            $item['show_submenu'] ?
                                $top_level_menu_slug :
                                null,
                            $item['page_title'],
                            $menu_item,
                            $capability,
                            $menu_slug,
                            $item['render_function']
                        );

                        if ( false !== $item['before_render_function'] ) {
                            add_action( "load-$hook", $item['before_render_function'] );
                        }
                    } else {
                        FS_Admin_Menu_Manager::add_subpage(
                            $item['show_submenu'] ?
                                $top_level_menu_slug :
                                null,
                            $item['page_title'],
                            $menu_item,
                            $capability,
                            $menu_slug,
                            array( $this, '' )
                        );
                    }

                    if ( $item['show_submenu'] && $is_first_submenu_item ) {
                        if ( $this->_is_network_active && ! empty( $this->_dynamically_added_top_level_page_hook_name ) ) {
                            /**
                             * If the top-level menu has been dynamically created, remove the first submenu item that
                             * WordPress automatically creates when there's no submenu item whose slug matches the
                             * parent's. In the following example, the `Awesome Plugin` submenu item will be removed.
                             *
                             * Awesome Plugin
                             *     - Awesome Plugin <-- we want to remove this since there's no real setting page for the top-level
                             *
                             * @author Leo Fajardo (@leorw)
                             */
                            remove_submenu_page( $top_level_menu_slug, $top_level_menu_slug );
                        }

                        $is_first_submenu_item = false;
                    }
                }
            }
        }