void setExpandedState(@Nullable TreePath path, boolean state) {
      if (path == null) {
        return;
      }
      if (!expandParentPaths(path)) {
        return;
      }
      if (state) {
        expandPath(path);
      }
      else {
        collapsePath(path);
      }
    }
void setExpandedState(@Nullable TreePath path, boolean state)