function handleHighlight(model, index) {
            var targetInfo = retrieveTargetInfo(payload, [HIGHLIGHT_ACTION], model);

            if (targetInfo) {
                payload.highlight = targetInfo.node;
            }
        }
Sort children nodes

@param {TreeNode[]}               children children of node to be sorted
@param {string | function | null} sort sort method
                                  See SunburstSeries.js for details.