@Override
      public void execute(Runnable command) {}
    }
  }

  private static final class NullByteSink extends ByteSink implements Serializable {
    private static final NullByteSink INSTANCE = new NullByteSink();

    @Override
    public OutputStream openStream() {
      return ByteStreams.nullOutputStream();
    }
  }

      @Override
      public void execute(Runnable command) {}
    }
  }

  private static final class NullByteSink extends ByteSink implements Serializable {
    private static final NullByteSink INSTANCE = new NullByteSink();

    @Override
    public OutputStream openStream() {
      return ByteStreams.nullOutputStream();
    }
  }