code: public void toIdFile(OutputStream os) throws IOException {
          BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os));
          for (TrieNodeData<T> child : root.children.values()) {
              child.writeIds(writer, new char[0]);// recursive
          }
          writer.close();
      }
docs: one entry per line. word first, then tab, then data