public INDArray flatten(INDArray[] inputs, String order) {
    Preconditions.checkArgument(inputs.length >= 1, "inputs has incorrect size/length. Expected: inputs.length >= 1, got %s", inputs.length);
    return Nd4j.exec(new org.nd4j.linalg.api.ops.custom.Flatten(inputs, order))[0];
  }