void IVisitor.VisitOnMerge(MergeStmt mergeStmt)
 {
     this.ParentExists(mergeStmt);
 }
 void IVisitor.VisitOnUsing(MergeStmt mergeStmt, int offset)
 {
     this.ParentExists(mergeStmt);
 }
 void IVisitor.VisitAfter(MergeStmt mergeStmt)
 {
     this.ParentExists(mergeStmt);
 }