docs: Node findNode(String fqn) {
          StringHolder sh=new StringHolder();
          Node n=findParentNode(fqn, sh, false);
          String child_name=sh.getValue();
  
          if(fqn == null || fqn.equals(SEPARATOR) || fqn != null && fqn.isEmpty())
              return root;
  
          if(n == null || child_name == null)
              return null;
          else
              return n.getChild(child_name);
      }