def _convert_round(builder, node, graph, err):
    """
    convert to CoreML Round Layer:
    https://github.com/apple/coremltools/blob/655b3be5cc0d42c3c4fa49f0f0e4a93a26b3e492/mlmodel/format/NeuralNetwork.proto#L5029
    """
    builder.add_round(name=node.name, input_name=node.inputs[0],
        output_name=node.outputs[0])
