def next_node
         peer = nil
         if !parent.nil? and parent.respond_to?(:children)
            index = parent.children.index(self)
            peer  = parent.children[index + 1]
         end
         peer
      end
def next_node
         peer = nil
         if !parent.nil? and parent.respond_to?(:children)
            index = parent.children.index(self)
            peer  = parent.children[index + 1]
         end
         peer
      end
This method retrieves a Node objects next peer node, returning nil
 if the Node has no previous peer.