// create RewriteRuleSubtreeStream from existing parse tree RewriteRuleSubtreeStream stream = new RewriteRuleSubtreeStream(parseTree); // add a new node to a subtree stream.Add(template, parentIndex, newTree); // replace an existing subtree with a new one stream.Replace(parentIndex, oldTree, newTree);In these examples, `parseTree` is an existing parse tree that has been generated by the Antlr parser. `template` is a template rule that specifies the new node to be added, `parentIndex` is the index of the parent node in the parse tree, and `newTree` is the new subtree that will be added or replace the old one. Overall, `Antlr.Runtime.Tree.RewriteRuleSubtreeStream` is a package library that offers developers greater control over the parse tree generated by the Antlr parser.