code: function getLinkGroupIndex(linksOption, axis) {
      var axisModel = axis.model;
      var dim = axis.dim;
      for (var i = 0; i < linksOption.length; i++) {
          var linkOption = linksOption[i] || {};
          if (checkPropInLink(linkOption[dim + 'AxisId'], axisModel.id)
              || checkPropInLink(linkOption[dim + 'AxisIndex'], axisModel.componentIndex)
              || checkPropInLink(linkOption[dim + 'AxisName'], axisModel.name)
          ) {
              return i;
          }
      }
  }
docs: For example:
  {
  axisPointer: {
  links: [{
  xAxisIndex: [2, 4],
  yAxisIndex: 'all'
  }, {
  xAxisId: ['a5', 'a7'],
  xAxisName: 'xxx'
  }]
  }
  }