code: public final JsonElement toJsonTree(T value) {
      try {
        JsonTreeWriter jsonWriter = new JsonTreeWriter();
        write(jsonWriter, value);
        return jsonWriter.get();
      } catch (IOException e) {
        throw new JsonIOException(e);
      }
    }
docs: Converts {@code value} to a JSON tree.
  
  @param value the Java object to convert. May be null.
  @return the converted JSON tree. May be {@link JsonNull}.
  @since 2.2