Как добавить штриховую сетку на диаграмму Google после загрузки?

google.charts.load('current', {
  packages: ['corechart', 'line']
}).then(function () {
  var data = new google.visualization.DataTable();
  data.addColumn('number', 'X');
  data.addColumn('number', 'Y0');
  data.addColumn('number', 'Y1');

  data.addRows([
    [0, 0, 0],    [1, 10, 5],   [2, 23, 15],  [3, 17, 9],   [4, 18, 10],  [5, 9, 5],
    [6, 11, 3],   [7, 27, 19],  [8, 33, 25],  [9, 40, 32],  [10, 32, 24], [11, 35, 27],
    [12, 30, 22], [13, 40, 32], [14, 42, 34], [15, 47, 39], [16, 44, 36], [17, 48, 40],
    [18, 52, 44], [19, 54, 46], [20, 42, 34], [21, 55, 47], [22, 56, 48], [23, 57, 49],
    [24, 60, 52], [25, 50, 42], [26, 52, 44], [27, 51, 43], [28, 49, 41], [29, 53, 45],
    [30, 55, 47], [31, 60, 52], [32, 61, 53], [33, 59, 51], [34, 62, 54], [35, 65, 57],
    [36, 62, 54], [37, 58, 50], [38, 55, 47], [39, 61, 53], [40, 64, 56], [41, 65, 57],
    [42, 63, 55], [43, 66, 58], [44, 67, 59], [45, 69, 61], [46, 69, 61], [47, 70, 62],
    [48, 72, 64], [49, 68, 60], [50, 66, 58], [51, 65, 57], [52, 67, 59], [53, 70, 62],
    [54, 71, 63], [55, 72, 64], [56, 73, 65], [57, 75, 67], [58, 70, 62], [59, 68, 60],
    [60, 64, 56], [61, 60, 52], [62, 65, 57], [63, 67, 59], [64, 68, 60], [65, 69, 61],
    [66, 70, 62], [67, 72, 64], [68, 75, 67], [69, 80, 72]
  ]);

  var options = {
    hAxis: {
      textStyle: { color: '#757575', },
      titleTextStyle: { color: '#757575',},
      minorGridlines: { color: 'transparent' },
      format : "MMM yy",
      gridlines: {color: '#f1efef',},
    },
    vAxis: {
      format: '#\'%\'',
      textStyle: { color: '#757575' },
      titleTextStyle: { color: '#757575' },
      minorGridlines: { color: 'transparent' },
      gridlines: {color: '#f1efef',},
    }
  };

  var chart = new google.visualization.LineChart(document.getElementById('chart_div'));

  google.visualization.events.addListener(chart, 'ready', function () {
    var gridLines = chart.getContainer().getElementsByTagName('rect');
    Array.prototype.forEach.call(gridLines, function(line) {
      if (line.getAttribute('fill') === '#f1efef') {
        line.setAttribute('fill', 'url(#pattern-fill) #f1efef');
      }
    });
  });

  chart.draw(data, options);
});

rect {
  stroke-dasharray: 10 5;
}

<script src="https://www.gstatic.com/charts/loader.js"></script>
<div id="chart_div"></div>
<svg style="width:0;height:0;position:absolute;" aria-hidden="true" focusable="false">
  <pattern id="pattern-fill" x="0" y="0" width="8" height="8" patternUnits="userSpaceOnUse" patternTransform="rotate(30)">
     <rect x="0" y="0" width="4" height="8" style="stroke: none; fill: #f1efef;" />
  </pattern>
</svg>