docs: private Map<String,INDArray> toPlaceholderMap(org.nd4j.linalg.dataset.api.MultiDataSet ds) {
          Map<String,INDArray> placeholders = new HashMap<>();
          int count = 0;
          for(String s : trainingConfig.getDataSetFeatureMapping()){
              placeholders.put(s, ds.getFeatures(count++));
          }
          count = 0;
          if(trainingConfig.getDataSetLabelMapping() != null) {
              //Labels may be null in some models (unsupervised etc)
              for (String s : trainingConfig.getDataSetLabelMapping()) {
                  placeholders.put(s, ds.getLabels(count++));
              }
          }
  
          if(trainingConfig.getDataSetFeatureMaskMapping() != null && trainingConfig.getDataSetFeatureMaskMapping().size() > 0){
              count = 0;
              for(String s : trainingConfig.getDataSetFeatureMaskMapping()){
                  if(s == null) {
                      count++;
                      continue;
                  }
                  placeholders.put(s, ds.getFeaturesMaskArray(count++));
              }
          }
  
          if(trainingConfig.getDataSetLabelMaskMapping() != null && trainingConfig.getDataSetLabelMaskMapping().size() > 0){
              count = 0;
              for(String s : trainingConfig.getDataSetLabelMaskMapping()){
                  if(s == null) {
                      count++;
                      continue;
                  }
                  placeholders.put(s, ds.getLabelsMaskArray(count++));
              }
          }
          return placeholders;
      }