code: func (af *aggFunction) Equal(b AggregationFunction, ctx context.Context) bool {
  	if af.GetName() != b.GetName() {
  		return false
  	}
  	if af.Distinct != b.IsDistinct() {
  		return false
  	}
  	if len(af.GetArgs()) == len(b.GetArgs()) {
  		for i, argA := range af.GetArgs() {
  			if !argA.Equal(b.GetArgs()[i], ctx) {
  				return false
  			}
  		}
  	}
  	return true
  }
docs: // Equal implements AggregationFunction interface.