docs: protected void checkActiveState(Widget child) {
          // Check if this widget has a valid href
          String href = child.getElement().getAttribute("href");
          String url = Window.Location.getHref();
          int pos = url.indexOf("#");
          String location = pos >= 0 ? url.substring(pos, url.length()) : "";
  
          if (!href.isEmpty() && location.startsWith(href)) {
              ListItem li = findListItemParent(child);
              if (li != null) {
                  makeActive(li);
              }
          } else if (child instanceof HasWidgets) {
              // Recursive check
              for (Widget w : (HasWidgets) child) {
                  checkActiveState(w);
              }
          }
      }