{
    "_yql_row_spec" = {"Type" = [
        "StructType";
        [
            [
                "first_null";
                [
                    "OptionalType";
                    [
                        "DataType";
                        "Uint32"
                    ]
                ]
            ];
            [
                "first_num";
                [
                    "OptionalType";
                    [
                        "DataType";
                        "Uint32"
                    ]
                ]
            ];
            [
                "second_null";
                [
                    "OptionalType";
                    [
                        "OptionalType";
                        [
                            "DataType";
                            "Uint32"
                        ]
                    ]
                ]
            ];
            [
                "second_num";
                [
                    "OptionalType";
                    [
                        "OptionalType";
                        [
                            "DataType";
                            "Uint32"
                        ]
                    ]
                ]
            ];
            [
                "third_null";
                [
                    "OptionalType";
                    [
                        "OptionalType";
                        [
                            "OptionalType";
                            [
                                "DataType";
                                "Uint32"
                            ]
                        ]
                    ]
                ]
            ];
            [
                "third_num";
                [
                    "OptionalType";
                    [
                        "OptionalType";
                        [
                            "OptionalType";
                            [
                                "DataType";
                                "Uint32"
                            ]
                        ]
                    ]
                ]
            ]
        ]
    ]};
}