function buildTooltipModel(modelCascade) {
    var resultModel = modelCascade.pop();
    while (modelCascade.length) {
        var tooltipOpt = modelCascade.pop();
        if (tooltipOpt) {
            if (Model.isInstance(tooltipOpt)) {
                tooltipOpt = tooltipOpt.get('tooltip', true);
            }
            // In each data item tooltip can be simply write:
            // {
            //  value: 10,
            //  tooltip: 'Something you need to know'
            // }
            if (typeof tooltipOpt === 'string') {
                tooltipOpt = {formatter: tooltipOpt};
            }
            resultModel = new Model(tooltipOpt, resultModel, resultModel.ecModel);
        }
    }
    return resultModel;
}
@action
@property {string} type
@property {number} seriesIndex
@property {number} dataIndex
@property {number} [x]
@property {number} [y]