function columnsAndFieldsFromYTrue(yTrue, nClasses) {
  return {
    columns: [yTrue],
    fields: [
      {
        name: GROUND_TRUTH_NAME,
        type: nClasses < 2 ? FEATURE_TYPE.NUMERICAL : FEATURE_TYPE.CATEGORICAL,
        role: FIELD_ROLE.GROUND_TRUTH,
        dataType: computeDataType(yTrue),
      },
    ],
  };
}
get columns and fields from ground truth data
@param {Array<Number|String>} yTrue ground truth
@return {Object} {columns - array of array of columns; fields: array of field metadata} in the same order