anchor.diff:      List<Tuple2<int, int>> columns,
       Map<String, CategoricalDataEncoderType> categoryNameToEncoder,
       Map<int, CategoricalDataEncoderType> categoryIndexToEncoder,
  -    void testContentFn(
  -        Matrix features, Matrix labels, List<String> headers)}) async {
  -  final data = CsvDataFrame.fromFile(fileName,
  +    void testContentFn(Matrix features, Matrix labels, List<String> headers,
  +        DataFrame dataFrame)}) async {
  +  final dataFrame = CsvDataFrame.fromFile(fileName,
         labelIdx: labelIdx,
         columns: columns,
         headerExists: headerExist,
         categoryNameToEncoder: categoryNameToEncoder,
         categoryIndexToEncoder: categoryIndexToEncoder,
     );
  -  final header = await data.header;
  -  final features = await data.features;
  -  final labels = await data.labels;
  +  final header = await dataFrame.header;
  +  final features = await dataFrame.features;
  +  final labels = await dataFrame.labels;
   
     expect(features.rowsNum, equals(rowNum));
     expect(labels.rowsNum, equals(rowNum));
   
  -  testContentFn(features, labels, header);
  +  testContentFn(features, labels, header, dataFrame);
   }
   
   void main() {
  
positive.code:             1: CategoricalDataEncoderType.ordinal,
              2: CategoricalDataEncoderType.oneHot,
            },
            testContentFn: (features, labels, header) {
              expect(header, isNull);
              expect(
                  features,
  
negative.code:             1: CategoricalDataEncoderType.ordinal,
              2: CategoricalDataEncoderType.oneHot,
            },
            testContentFn: (features, labels, header, dataFrame) {
              expect(header,
                  equals(['feature_1', 'feature_2', 'feature_3', 'score']));
              expect(
  