private void createSyncingSubscriptionService(
      final Synchronizer synchronizer, final SubscriptionManager subscriptionManager) {
    new SyncingSubscriptionService(subscriptionManager, synchronizer);
  }
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