static _groupItemFilter(item, idx, allItems, filteredItems) {
      if (item.isGroupItem) {
        let groupHasFilteredItems;
        while (allItems[idx] && !allItems[idx].isGroupItem && !groupHasFilteredItems) {
          groupHasFilteredItems = filteredItems.indexOf(allItems[idx]) !== -1;
          idx++;
        }
        return groupHasFilteredItems;
      }
    }
Returns true if the group header should be shown (if there is a filtered suggestion item for this group item)

@private