code: public static DefaultMutableTreeNode leftShift(DefaultMutableTreeNode self, DefaultMutableTreeNode node) {
          self.add(node);
          return self;
      }
docs: Overloads the left shift operator to provide an easy way to add
  nodes to a DefaultMutableTreeNode.<p>
  
  @param self a DefaultMutableTreeNode
  @param node a node to be added to the treeNode.
  @return same treeNode, after the value was added to it.
  @since 1.6.4