当值相同时，如何单独显示行而不重叠

Question

使用谷歌图表API（折线图）。我有相同的值集，用于绘制服务器和运输的行，因为值相同，两行重叠，如演示https://plnkr.co/edit/PNA1XQapRzvxGfm7behd?p=preview所示

有没有一种方法可以让我们看到两条线而不是重叠它们具有相同的值？

angular.module('myApp', ['googlechart'])
  .controller('myController', function($scope) {
    var chart1 = {};
    chart1.type = "LineChart";
    chart1.displayed = false;
    chart1.data = {
      "cols": [{
        id: "month",
        label: "Month",
        type: "string"
      }, {
        id: "laptop-id",
        label: "Laptop",
        type: "number"
      }, {
        id: "desktop-id",
        label: "Desktop",
        type: "number"
      }, {
        id: "server-id",
        label: "Server",
        type: "number"
      }, {
        id: "cost-id",
        label: "Shipping",
        type: "number"
      }],
      "rows": [{
        c: [{
          v: "January"
        }, {
          v: 19,
         }, {
          v: 12,
         }, {
          v: 7, //server
         }, {
          v: 7  //shipping
        }]
      }, {
        c: [{
          v: "February"
        }, {
          v: 13
        }, {
          v: 1,
         }, {
          v: 12  //server
        }, {
          v: 12  //shipping
        }]
      }, {
        c: [{
            v: "March"
          }, {
            v: 24
          }, {
            v: 5
          }, { 
            v: 11  //server
          }, {
            v: 11  //shipping
          }
        ]
      }]
    };
    chart1.options = {
      "title": "Sales per month",
      "colors": ['#0000FF', '#009900', '#CC0000', '#DD9900'],
      "defaultColors": ['#0000FF', '#009900', '#CC0000', '#DD9900'],
      "isStacked": "percent",
       focusTarget: 'category',
      "fill": 20,
      "displayExactValues": true,
      "vAxis": {
        "title": "Sales unit",
        "gridlines": {
          "count": 10
        }
      },
      "hAxis": {
        "title": "Date"
      }
    };
    chart1.view = {
      columns: [0, 1, 2, 3, 4]
    };
    $scope.myChart = chart1;
  });