Google Chart Pie Chart

HTML

<script src="https://www.google.com/jsapi"></script>
<div id="chart_div" style="width: 900px; height: 500px;"></div>

<div id="chart_div2" style="width: 900px; height: 500px;"></div>

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<div id='download_png'></div>
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<canvas id="product-image" width="800px" height="800px"></canvas>

JavaScript

google.load("visualization", "1", {packages:["corechart"]});
      google.setOnLoadCallback(drawChart);
      function drawChart() {
        var data = google.visualization.arrayToDataTable([
          ['Task', 'Hours per Day'],
          ['Work',     11],
          ['Eat',      2],
          ['Commute',  2],
          ['Watch TV', 2],
          ['Sleep',    7]
        ]);

        var options = {
          title: 'My Daily Activities'
        };

var chartObjs = [];

        var chart = new google.visualization.PieChart(document.getElementById('chart_div'));
       
        
        chartObjs.push(chart);
        
         var chart2 = new google.visualization.ColumnChart(document.getElementById('chart_div2'));
        chart2.draw(data, options);
      
      
      chartObjs.push(chart2)
      
      var pngDataArr= [];
      chartObjs.forEach(function(obj, i) {
						google.visualization.events.addListener(obj, 'ready', function () {
	    					console.log("here")
                var thisChart = obj;
                 console.log("thisChart")
                console.log(thisChart)
	    					if (thisChart) {
								    var image = thisChart.getImageURI();
									  pngDataArr.push(image);
								
                    var canvas = document.getElementById("product-image");
								    console.log(canvas)
                    if (canvas) {
									       var context = canvas.getContext('2d');
									       console.log(pngDataArr);
                         pngDataArr.forEach(function(src, index) {
									            img = new Image;
									            img.onload = function() {
									                context.drawImage(this, index * this.width, index * this.width)
									 	              img.src = src;
									            }
									       });
									
                        var png = document.getElementById('download_png');
									      png.innerHTML = '<a target="_blank" download="AwesomeChart.png" href="' + canvas.toDataURL() + '"><button class="fa...