docs: public static Pair<INDArray[], INDArray[]> mergeFeatures(@NonNull INDArray[][] featuresToMerge, INDArray[][] featureMasksToMerge) {
          int nInArrs = featuresToMerge[0].length;
          INDArray[] outF = new INDArray[nInArrs];
          INDArray[] outM = null;
  
          for (int i = 0; i < nInArrs; i++) {
              Pair<INDArray, INDArray> p = mergeFeatures(featuresToMerge, featureMasksToMerge, i);
              outF[i] = p.getFirst();
              if (p.getSecond() != null) {
                  if (outM == null) {
                      outM = new INDArray[nInArrs];
                  }
                  outM[i] = p.getSecond();
              }
          }
          return new Pair<>(outF, outM);
      }