code: async function createColumns(workSheetInfo, fieldNames, startIndex) {
      if (!util.isArray(fieldNames)) {
          return Promise.reject(
              new Error('Field names should be specified in array format')
          );
      }
  
      let promises = fieldNames.map(fieldName => {
          let payload = api.converter.createFieldRequest(fieldName, ++startIndex);
          let requestPayload = util._extend(
              {body: payload, cellId: 'R1C' + startIndex},
              workSheetInfo
          );
  
          return executeRequest('create_field', requestPayload);
      });
  
      let response = await Promise.all(promises);
      cache.clear();
      return response;
  }
docs: Create field names (first row) in the sheet
  
  @param {object} workSheetInfo SheetID and worksheetID
  @param {array} fieldNames Name of the fields
  @param {number} startIndex First column of new rows