code: function(parent, records, suppressEvent) {
          var me = this,
              insertIndex = me.indexOf(parent) + 1,
              toAdd = [];
  
          // Used by the TreeView to bracket recursive expand & collapse ops
          // and refresh the size. This is most effective when folder nodes are loaded,
          // and this method is able to recurse.
          if (!suppressEvent) {
              me.fireEvent('beforeexpand', parent, records, insertIndex);
          }
  
          me.handleNodeExpand(parent, records, toAdd);
  
          // The add event from this insertion is handled by TreeView.onAdd.
          // That implementation calls parent and then ensures the previous sibling's joining lines are correct.
          // The datachanged event is relayed by the TreeStore. Internally, that's not used.
          me.insert(insertIndex, toAdd);
  
          // Triggers the TreeView's onExpand method which calls refreshSize,
          // and fires its afteritemexpand event
          if (!suppressEvent) {
              me.fireEvent('expand', parent, records);
          }
      }
docs: Triggered by a NodeInterface's bubbled "expand" event.