Function getDatasetModel

libs/echarts/echarts.simple.js:21082–21093

* If return null/undefined, indicate that should not use datasetModel.

(seriesModel)

 * If return null/undefined, indicate that should not use datasetModel.
 */
function getDatasetModel(seriesModel) {
    var option = seriesModel.option;
    // Caution: consider the scenario:
    // A dataset is declared and a series is not expected to use the dataset,
    // and at the beginning `setOption({series: { noData })` (just prepare other
    // option but no data), then `setOption({series: {data: [...]}); In this case,
    // the user should set an empty array to avoid that dataset is used by default.
    var thisData = option.data;
    if (!thisData) {
        return seriesModel.ecModel.getComponent('dataset', option.datasetIndex || 0);
    }
}

/**
 * The rule should not be complex, otherwise user might not