code: public Object get(String fqn, String key) {
          Node n=findNode(fqn);
  
          if(n == null) return null;
          return n.getData(key);
      }
docs: Finds a node given its name and returns the value associated with a given key in its {@code data}
  map. Returns null if the node was not found in the tree or the key was not found in the hashmap.
  @param fqn The fully qualified name of the node.
  @param key The key.