code: public void fit(MultiDataSet multiDataSet) {
          fit(multiDataSet.getFeatures(), multiDataSet.getLabels(), multiDataSet.getFeaturesMaskArrays(),
                  multiDataSet.getLabelsMaskArrays());
          if (multiDataSet.hasMaskArrays())
              clearLayerMaskArrays();
      }
docs: Fit the ComputationGraph using a MultiDataSet