code: function create(ecModel, api) {
      var singles = [];
  
      ecModel.eachComponent('singleAxis', function (axisModel, idx) {
  
          var single = new Single(axisModel, ecModel, api);
          single.name = 'single_' + idx;
          single.resize(axisModel, api);
          axisModel.coordinateSystem = single;
          singles.push(single);
  
      });
  
      ecModel.eachSeries(function (seriesModel) {
          if (seriesModel.get('coordinateSystem') === 'singleAxis') {
              var singleAxisModel = ecModel.queryComponents({
                  mainType: 'singleAxis',
                  index: seriesModel.get('singleAxisIndex'),
                  id: seriesModel.get('singleAxisId')
              })[0];
              seriesModel.coordinateSystem = singleAxisModel && singleAxisModel.coordinateSystem;
          }
      });
  
      return singles;
  }
docs: Create single coordinate system and inject it into seriesModel.
  
  @param {module:echarts/model/Global} ecModel
  @param {module:echarts/ExtensionAPI} api
  @return {Array.<module:echarts/coord/single/Single>}