code: function groupBy(item) {
      if (item instanceof Raw) {
        return this.groupByRaw.apply(this, arguments);
      }
      this._statements.push({
        grouping: 'group',
        type: 'groupByBasic',
        value: normalizeArr.apply(null, arguments)
      });
      return this;
    }
docs: Adds a `group by` clause to the query.