text: public virtual SmallDocSet Union(SmallDocSet other){SmallDocSet bigger;SmallDocSet smaller;if (other.intSet.Count > this.intSet.Count){bigger = other;smaller = this;}else{bigger = this;smaller = other;}foreach (int v in smaller.intSet.Keys){if (v == smaller.intSet.EmptyVal){continue;}bigger.Set(v);}return bigger;}