private void createNewBlockHeadersSubscriptionService(
      final Blockchain blockchain,
      final BlockchainQueries blockchainQueries,
      final SubscriptionManager subscriptionManager) {
    final NewBlockHeadersSubscriptionService newBlockHeadersSubscriptionService =
        new NewBlockHeadersSubscriptionService(subscriptionManager, blockchainQueries);

    blockchain.observeBlockAdded(newBlockHeadersSubscriptionService);
  }
Gets fixed nodes. Visible for testing.

@param someFixedNodes the fixed nodes
@param moreFixedNodes nodes added to fixed nodes
@return the fixed and more nodes combined
app/src/main/java/org/hyperledger/besu/RunnerBuilder.java