def add_node(node)
      if node.respond_to?(:to_sym)
        node = Woodhouse::Layout::Node.new(node.to_sym)  
      end
      expect_arg :node, Woodhouse::Layout::Node, node
      @nodes << node
      node
    end
def add_node(node)
      if node.respond_to?(:to_sym)
        node = Woodhouse::Layout::Node.new(node.to_sym)  
      end
      expect_arg :node, Woodhouse::Layout::Node, node
      @nodes << node
      node
    end
Adds a Node to this layout. If +node+ is a Symbol, a Node will be
 automatically created with that name.

   # Example:

   layout.add_node Woodhouse::Layout::Node.new(:isis)

   # Is equivalent to

   layout.add_node :isis