WP_Import::process_menu_item PHP Method

        function process_menu_item($item)
        {
            // skip draft, orphaned menu items
            if ('draft' == $item['status']) {
                return;
            }
            $menu_slug = false;
            if (isset($item['terms'])) {
                // loop through terms, assume first nav_menu term is correct menu
                foreach ($item['terms'] as $term) {
                    if ('nav_menu' == $term['domain']) {
                        $menu_slug = $term['slug'];
                        break;
                    }
                }
            }
            // no nav_menu term associated with this menu item
            if (!$menu_slug) {
                _e('Menu item skipped due to missing menu slug', 'wordpress-importer');
                echo '<br />';
                return;
            }
            $menu_id = term_exists($menu_slug, 'nav_menu');
            if (!$menu_id) {
                printf(__('Menu item skipped due to invalid menu slug: %s', 'wordpress-importer'), esc_html($menu_slug));
                echo '<br />';
                return;
            } else {
                $menu_id = is_array($menu_id) ? $menu_id['term_id'] : $menu_id;
            }
            foreach ($item['postmeta'] as $meta) {
                ${$meta}['key'] = $meta['value'];
            }
            if ('taxonomy' == $_menu_item_type && isset($this->processed_terms[intval($_menu_item_object_id)])) {
                $_menu_item_object_id = $this->processed_terms[intval($_menu_item_object_id)];
            } else {
                if ('post_type' == $_menu_item_type && isset($this->processed_posts[intval($_menu_item_object_id)])) {
                    $_menu_item_object_id = $this->processed_posts[intval($_menu_item_object_id)];
                } else {
                    if ('custom' != $_menu_item_type) {
                        // associated object is missing or not imported yet, we'll retry later
                        $this->missing_menu_items[] = $item;
                        return;
                    }
                }
            }
            if (isset($this->processed_menu_items[intval($_menu_item_menu_item_parent)])) {
                $_menu_item_menu_item_parent = $this->processed_menu_items[intval($_menu_item_menu_item_parent)];
            } else {
                if ($_menu_item_menu_item_parent) {
                    $this->menu_item_orphans[intval($item['post_id'])] = (int) $_menu_item_menu_item_parent;
                    $_menu_item_menu_item_parent = 0;
                }
            }
            // wp_update_nav_menu_item expects CSS classes as a space separated string
            $_menu_item_classes = maybe_unserialize($_menu_item_classes);
            if (is_array($_menu_item_classes)) {
                $_menu_item_classes = implode(' ', $_menu_item_classes);
            }
            $args = array('menu-item-object-id' => $_menu_item_object_id, 'menu-item-object' => $_menu_item_object, 'menu-item-parent-id' => $_menu_item_menu_item_parent, 'menu-item-position' => intval($item['menu_order']), 'menu-item-type' => $_menu_item_type, 'menu-item-title' => $item['post_title'], 'menu-item-url' => $_menu_item_url, 'menu-item-description' => $item['post_content'], 'menu-item-attr-title' => $item['post_excerpt'], 'menu-item-target' => $_menu_item_target, 'menu-item-classes' => $_menu_item_classes, 'menu-item-xfn' => $_menu_item_xfn, 'menu-item-status' => $item['status']);
            $id = wp_update_nav_menu_item($menu_id, 0, $args);
            if ($id && !is_wp_error($id)) {
                $this->processed_menu_items[intval($item['post_id'])] = (int) $id;
            }
        }

 public function process_menu_item($item)
 {
     $this->updateStats();
     parent::process_menu_item($item);
     // We need to step in to import custom meta assigned to a menu item because WP Importer won't do it for us
     // get the post (nav-menu-item) id
     $id = intval($item['post_id']);
     // check if it has been imported by WP Importer
     $id = empty($this->processed_menu_items[$id]) ? false : $this->processed_menu_items[$id];
     if ($id && is_array($item['postmeta'])) {
         // it seems it has, now cycle all metas to search ours
         foreach ($item['postmeta'] as $meta) {
             if ($meta['key'] === PE_THEME_META) {
                 // bingo, update the menu item meta
                 update_post_meta($id, PE_THEME_META, maybe_unserialize($meta['value']));
                 break;
             }
         }
     }
 }