code: function(root, /* private */ preventLoad) {
          var me = this,
              model = me.model,
              idProperty = model.prototype.idProperty
  
          root = root || {};
          if (!root.isModel) {
              root = Ext.apply({}, root);
              // create a default rootNode and create internal data struct.
              Ext.applyIf(root, {
                  id: me.defaultRootId,
                  text: me.defaultRootText,
                  allowDrag: false
              });
              if (root[idProperty] === undefined) {
                  root[idProperty] = me.defaultRootId;
              }
              Ext.data.NodeInterface.decorate(model);
              root = Ext.ModelManager.create(root, model);
          } else if (root.isModel && !root.isNode) {
              Ext.data.NodeInterface.decorate(model);
          }
  
  
          // Because we have decorated the model with new fields,
          // we need to build new extactor functions on the reader.
          me.getProxy().getReader().buildExtractors(true);
  
          // When we add the root to the tree, it will automaticaly get the NodeInterface
          me.tree.setRootNode(root);
  
          // If the user has set expanded: true on the root, we want to call the expand function to kick off
          // an expand process, so clear the expanded status and call expand.
          // Upon receipt, the expansion process is the most efficient way of processing the
          // returned nodes and putting them into the NodeStore in one block.
          // Appending a node to an expanded node is expensive - the NodeStore and UI are updated.
          if (preventLoad !== true && !root.isLoaded() && (me.autoLoad === true || root.isExpanded())) {
              root.data.expanded = false;
              root.expand();
          }
  
          return root;
      }
docs: Sets the root node for this store.  See also the {@link #root} config option.
  @param {Ext.data.Model/Ext.data.NodeInterface/Object} root
  @return {Ext.data.NodeInterface} The new root