code: @Override
    public void registerCompletesEventuallyProviderKeeper(final CompletesEventuallyProviderKeeper keeper) {
      if (this.completesProviderKeeper != null) {
        this.completesProviderKeeper.close();
      }
      this.completesProviderKeeper = keeper;
    }
docs: Registers the {@code CompletesEventuallyProviderKeeper} plugin.
  @param keeper the {@code CompletesEventuallyProviderKeeper} to register