code: function(node1, node2) {
  			node1 = node1 instanceof gui.Spirit ? node1.element : node1;
  			node2 = node2 instanceof gui.Spirit ? node2.element : node2;
  			return node1.compareDocumentPosition(node2);
  		}
docs: Compare document position of two nodes.
  @see http://mdn.io/compareDocumentPosition
  @param {Node|gui.Spirit} node1
  @param {Node|gui.Spirit} node2
  @returns {number}