code: func NewAggregateConstructor(aggDescription string, aggFunc crossSeriesAggFunc) func() GraphiteFunc {
  	return func() GraphiteFunc {
  		return &FuncAggregate{agg: seriesAggregator{function: aggFunc, name: aggDescription}}
  	}
  }
docs: // NewAggregateConstructor takes an agg string and returns a constructor function