code: function(nodeModel, excludes) {
  			if(nodeModel){
  				this._expandRecursively(nodeModel, excludes);
  			} else {
  				if(!this._navHandler){
  					return;
  				}
  				//We already know what the top level children is under the root, from the navigation handler.
  				var topLevelNodes = this._navHandler.getTopLevelNodes();
  				for (var i = 0; i < topLevelNodes.length ; i++){
  					this._expandRecursively(topLevelNodes[i], excludes);
  				}
  			}
  		}
docs: Expand all the nodes under a node in the explorer
  @param nodeModel {Object} the node model to be expanded. If not provided the whole tree is expanded recursively