code: function(columnNames) {
          var columnModel = this.columnModel;
          var mergedColumnNames = _.pluck(columnModel.get('complexHeaderColumns'), 'name');
  
          return _.filter(mergedColumnNames, function(mergedColumnName) {
              var unitColumnNames = columnModel.getUnitColumnNamesIfMerged(mergedColumnName);
  
              return _.every(unitColumnNames, function(name) {
                  return _.contains(columnNames, name);
              });
          });
      }
docs: Returns an array of names of merged-column which contains every column name in the given array.
  @param {Array.<String>} columnNames - an array of column names to test
  @returns {Array.<String>}
  @private