code: public void readFields(DataInput in) throws IOException {
          DataInputStream dis = new DataInputStream(new DataInputWrapperStream(in));
          byte header = dis.readByte();
          if (header != NDARRAY_SER_VERSION_HEADER && header != NDARRAY_SER_VERSION_HEADER_NULL) {
              throw new IllegalStateException("Unexpected NDArrayWritable version header - stream corrupt?");
          }
  
          if (header == NDARRAY_SER_VERSION_HEADER_NULL) {
              array = null;
              return;
          }
  
          array = Nd4j.read(dis);
          hash = null;
      }
docs: Deserialize into a row vector of default type.