docs: function renderItem (element, data, updating) {
      _(this).onItemRender(element, {
          ...data.original,
          expanded: isExpanded.call(this, data.id),
          indent: calculateLevel.call(this, data),
          toggle: () => {
              // Check to see if this item is expanded or not
              let expanded = isExpanded.call(this, data.id);
              if (expanded) {
                  collapseItem.call(this, data);
              } else {
                  expandItem.call(this, data);
              }
  
              // Each time we expand or collapse we need to re-request data.
              requestData.call(this);
          }
      }, updating);
  }