code: function _updateColspan(tableData, startColIndex, endColIndex) {
    tableData.forEach(rowData => {
      util.range(startColIndex, endColIndex + 1).forEach(colIndex => {
        const cellData = rowData [colIndex];
  
        if (util.isExisty(cellData.colMergeWith)) {
          const merger = rowData [cellData.colMergeWith];
  
          if (merger.colspan) {
            merger.colspan -= 1;
          }
        } else if (cellData.colspan > 1) {
          const lastMergedCellIndex = colIndex + cellData.colspan - 1;
  
          cellData.colspan -= (endColIndex - colIndex + 1);
  
          if (lastMergedCellIndex > endColIndex) {
            rowData [endColIndex + 1] = util.extend({}, cellData);
          }
        }
      });
    });
  }
docs: Update colspan to col merger.
  @param {Array.<Array.<object>>} tableData - table data
  @param {number} startColIndex - start col index
  @param {number} endColIndex - end col index
  @private