code: public UNode addMapNode(String name, String tagName) {
          return addChildNode(UNode.createMapNode(name, tagName));
      }
docs: Create a new MAP node with the given name and tag name add it as a child of this
  node. This node must be a MAP or ARRAY. This is a convenience method that calls
  {@link UNode#createMapNode(String, String)} and then {@link #addChildNode(UNode)}.
  
  @param  name     Name of new MAP node.
  @param  tagName  Tag name of new MAP node (for XML).
  @return          New MAP node, added as a child of this node.