如何在chart.js中添加额外的图例项？

var myChart = new Chart(ctx, {
    type: 'bar',
    data: data,
    options: options
});

var options = {
    legend: {
        display: true,
        labels: {
            fontColor: 'black',
            fontSize: 12
        }
    }
};

var options = {
    legend: {
        display: true,
        labels: {
            fontColor: 'black',
            fontSize: 12,
            generateLabels: function(chart) {
                var labels = [];
                labels.push({
                    text: '自定义图例项1',
                    fillStyle: 'red'
                });
                labels.push({
                    text: '自定义图例项2',
                    fillStyle: 'blue'
                });
                return labels;
            }
        }
    }
};

myChart.options = options;
myChart.update();