code: func (a *AggregateResult) Sort(field string) {
  	if !startsUpper(field) {
  		panic("The first letter of a field must be upper-case")
  	}
  	if a.sortby == field {
  		// already sorted
  		return
  	}
  
  	a.sortby = field
  	sort.Sort((*aggregateResultSort)(a))
  }
docs: // Sort sorts the aggregate reduction by the passed in field in ascending order
  // Sort is called automatically by calls to Min / Max to get the min and max values