def ir_version():
    """
    Returns the preferred `IR_VERSION
    <https://github.com/onnx/onnx/blob/master/docs/IR.md#onnx-versioning>`_.

    .. runpython::
        :showcode:

        from mlprodict.tools.asv_options_helper import ir_version
        print(ir_version())
    """
    return [6]
