code: public <K> JavaPairRDD<K, INDArray> feedForwardWithMaskAndKey(JavaPairRDD<K, Tuple2<INDArray,INDArray>> featuresDataAndMask, int batchSize) {
          return featuresDataAndMask
                  .mapPartitionsToPair(new FeedForwardWithKeyFunction<K>(sc.broadcast(network.params()),
                          sc.broadcast(conf.toJson()), batchSize));
      }
docs: Feed-forward the specified data (and optionally mask array), with the given keys. i.e., get the network
  output/predictions for the specified data
  
  @param featuresDataAndMask Features data to feed through the network. The Tuple2 is of the network input (features),
  and optionally the feature mask arrays
  @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 (and optionally mask), by key