throw new UnsupportedOperationException();
      }
    };
  }

  @J2ktIncompatible
  @GwtIncompatible // Writer
  static Writer separatingWriter(Writer delegate, String separator, int afterEveryChars) {
    Appendable separatingAppendable = separatingAppendable(delegate, separator, afterEveryChars);
    return new Writer() {
      @Override