docs: static CharOutput stringBuilderOutput(int initialSize) {
      final StringBuilder builder = new StringBuilder(initialSize);
      return new CharOutput() {
  
        @Override
        public void write(char c) {
          builder.append(c);
        }
  
        @Override
        public void flush() {}
  
        @Override
        public void close() {}
  
        @Override
        public String toString() {
          return builder.toString();
        }
      };
    }