code: function getViewRect(seriesModel, api) {
      return layout.getLayoutRect(
          seriesModel.getBoxLayoutParams(), {
              width: api.getWidth(),
              height: api.getHeight()
          }
      );
  }
docs: Get the layout position of the whole view
  
  @param {module:echarts/model/Series} seriesModel  the model object of sankey series
  @param {module:echarts/ExtensionAPI} api  provide the API list that the developer can call
  @return {module:zrender/core/BoundingRect}  size of rect to draw the sankey view