code: @GwtIncompatible("ByteSink,CharSink")
    public final ByteSink encodingSink(final CharSink encodedSink) {
      checkNotNull(encodedSink);
      return new ByteSink() {
        @Override
        public OutputStream openStream() throws IOException {
          return encodingStream(encodedSink.openStream());
        }
      };
    }
docs: Returns a {@code ByteSink} that writes base-encoded bytes to the specified {@code CharSink}.