code: public <K> JavaPairRDD<K, INDArray> feedForwardWithKeySingle(JavaPairRDD<K, INDArray> featuresData, int batchSize) {
          if (network.getNumInputArrays() != 1 || network.getNumOutputArrays() != 1) {
              throw new IllegalStateException(
                              "Cannot use this method with computation graphs with more than 1 input or output "
                                              + "( has: " + network.getNumInputArrays() + " inputs, "
                                              + network.getNumOutputArrays() + " outputs");
          }
          PairToArrayPair<K> p = new PairToArrayPair<>();
          JavaPairRDD<K, INDArray[]> rdd = featuresData.mapToPair(p);
          return feedForwardWithKey(rdd, batchSize).mapToPair(new ArrayPairToPair<K>());
      }
docs: Feed-forward the specified data, with the given keys. i.e., get the network output/predictions for the specified data
  
  @param featuresData Features data to feed through the network
  @param batchSize    Batch size to use when doing feed forward operations
  @param <K>          Type of data for key - may be anything
  @return             Network output given the input, by key