code: function(flag, opts) {
  			flag = flag !== false;
  			this.visit(function(node) {
  				if (
  					node.hasChildren() !== false &&
  					node.isExpanded() !== flag
  				) {
  					node.setExpanded(flag, opts);
  				}
  			});
  		}
docs: Expand (or collapse) all parent nodes.
  
  This convenience method uses `tree.visit()` and `tree.setExpanded()`
  internally.
  
  @param {boolean} [flag=true] pass false to collapse
  @param {object} [opts] passed to setExpanded()
  @since 2.30