code: function(node, textNodeMap) {
                  if (canExpando || node.nodeType !== 3) {
                      return node[expando];
                  } else {
                      // The nodeList has a specific collection for HTMLTextNodes for 
                      // (older) browsers that do not support expando properties.
                      for (var textNodeID in textNodeMap) {
                          if (textNodeMap[textNodeID] === node) {
                              return textNodeID;
                          }
                      }
                  }
              }
docs: A mapping of element ids to nodeList id allowing us to quickly find an element that needs to be replaced when updated.