{
    "_yql_row_spec"={
        "Type"=["StructType";[
            ["key";["DataType";"String"]];
            ["subkey";["DataType";"String"]];
            ["value";["DataType";"String"]];
        ]];
        "DefaultValues"={
            "key"="\"def_key\"";
            "subkey"="\"def_subkey\"";
            "value"="\"def_value\"";
        };
    };
    "schema"=<"strict" = %true> [
        {"type"="string"; "name"="key"};
        {"type"="string"; "name"="subkey"};
        {"type"="string"; "name"="value"}
    ]
}