谷歌饼图

我尝试在我的网站上创建一个饼图，我发现示例代码谷歌饼图

<div id="piechart"></div> 

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script> 

<script type="text/javascript"> 
    // Load google charts 
    google.charts.load('current', {'packages':['corechart']}); 
    google.charts.setOnLoadCallback(drawChart); 

    // Draw the chart and set the chart values 
    function drawChart() { 
     var data = google.visualization.arrayToDataTable([ 
      ['Task', 'Hours per Day'], 
      ['Work', 8], 
      ['Eat', 2], 
      ['TV', 4], 
      ['Gym', 2], 
      ['Sleep', 8] 
     ]); 

     // Optional; add a title and set the width and height of the chart 
     var options = {'title':'My Average Day', 'width':550, 'height':400}; 

     // Display the chart inside the <div> element with id="piechart" 
     var chart = new google.visualization.PieChart(document.getElementById('piechart')); 
     chart.draw(data, options); 
    } 
</script>

（https://www.w3schools.com/howto/tryit.asp?filename=tryhow_google_pie_chart）

但我只得到一个错误信息：