code: public Table aggregate(String colName1, AggregateFunction<?,?>... functions) {
          ArrayListMultimap<String, AggregateFunction<?,?>> columnFunctionMap = ArrayListMultimap.create();
          columnFunctionMap.putAll(colName1, Lists.newArrayList(functions));
          return aggregate(columnFunctionMap);
      }
docs: Applies the given aggregation to the given column.
  The apply and combine steps of a split-apply-combine.