code: function _updateColMergeWith(targetRows, startColIndex, endColIndex, colMergeWith) {
    const limitColIndex = endColIndex + 1;
  
    targetRows.forEach(rowData => {
      rowData.slice(startColIndex, limitColIndex).forEach(cellData => {
        cellData.colMergeWith = colMergeWith;
      });
    });
  }
docs: Update colMergeWith property of target rows for column merge.
  @param {Array.<Array.<object>>} targetRows - target rows
  @param {number} startColIndex - start column index
  @param {number} endColIndex - end column index
  @param {number} colMergeWith - index of column merger
  @private