title: How to add amgraph in update chart in amcharts
body: <p>I want to show multiple line graphs in stepline amchart. But the issue is 
     for one response , I need to show one Line graph only, for the same chart for 
     another response I need to show 2 line graphs. </p>
  
  <pre><code>     this.timeChart = this.AmCharts.makeChart("chartdiv2", {
    "type": "serial",
    "theme": "light",
    "marginRight": 80,
    "autoMarginOffset": 20,
    "marginTop": 7,
    "dataProvider": chartData,
  "valueAxes": [{
      "axisAlpha": 0,
      "position": "left",
      "title": "Response Count",
      "autoGridCount": false,
      "gridCount": 5,
      "gridAlpha": 0
  }],
  "graphs": [{
      "id": "g1",
      "balloonText": "[[title]]&lt;br&gt;[[category]]&lt;br&gt;&lt;b&gt;[[value]] &lt;/b&gt;",
      "lineThickness": 1,
      "bullet": "square",
      "type": "step",
      "bulletAlpha": 0,
      "bulletSize": 4,
      "bulletBorderAlpha": 0,
      "valueField": "members",
      'lineColor': 'pink',
      'title': 'Member Response',
  },
  </code></pre>
  
  <p>After this I want to add another graph object in Update Chart.
  How to do that.</p>